Lowercase TargetOS (#80164)

Follow-up on #32451
Follow-up on #80074

In #43651, the "Windows" OS name was lowercased to achieve target frameworks with RIDs in them. At that time, the original plan was to lowercase all TargetOS values but that had to be cut because of resources. This PR finishes that and updates build systems, YML, markdowns and managed components.

To not break existing developer workflows, the passed-in -os value is automatically lower-cased in the script entry points and validated in the msbuild entry point.

.devcontainer/scripts/onCreateCommand.sh

@@ -16,7 +16,7 @@ case "$opt" in
         # prebuild for WASM, so it is ready for wasm development
         make -C src/mono/wasm provision-wasm
         export EMSDK_PATH=$PWD/src/mono/wasm/emsdk
-        ./build.sh mono+libs -os Browser -c Release
+        ./build.sh mono+libs -os browser -c Release
 
         # install dotnet-serve for running wasm samples
         ./dotnet.sh tool install dotnet-serve --tool-path ./.dotnet-tools-global

Directory.Build.props

@@ -10,18 +10,18 @@
   </PropertyGroup>
 
   <PropertyGroup Label="CalculateTargetOS">
-    <_hostOS>Linux</_hostOS>
-    <_hostOS Condition="$([MSBuild]::IsOSPlatform('OSX'))">OSX</_hostOS>
-    <_hostOS Condition="$([MSBuild]::IsOSPlatform('FREEBSD'))">FreeBSD</_hostOS>
-    <_hostOS Condition="$([MSBuild]::IsOSPlatform('NETBSD'))">NetBSD</_hostOS>
+    <_hostOS>linux</_hostOS>
+    <_hostOS Condition="$([MSBuild]::IsOSPlatform('OSX'))">osx</_hostOS>
+    <_hostOS Condition="$([MSBuild]::IsOSPlatform('FREEBSD'))">freebsd</_hostOS>
+    <_hostOS Condition="$([MSBuild]::IsOSPlatform('NETBSD'))">netbsd</_hostOS>
     <_hostOS Condition="$([MSBuild]::IsOSPlatform('ILLUMOS'))">illumos</_hostOS>
-    <_hostOS Condition="$([MSBuild]::IsOSPlatform('SOLARIS'))">Solaris</_hostOS>
+    <_hostOS Condition="$([MSBuild]::IsOSPlatform('SOLARIS'))">solaris</_hostOS>
     <_hostOS Condition="$([MSBuild]::IsOSPlatform('WINDOWS'))">windows</_hostOS>
     <HostOS>$(_hostOS)</HostOS>
     <TargetOS Condition="'$(TargetOS)' == '' and '$(RuntimeIdentifier)' == 'browser-wasm'">browser</TargetOS>
     <TargetOS Condition="'$(TargetOS)' == ''">$(_hostOS)</TargetOS>
-    <TargetsMobile Condition="'$(TargetOS)' == 'iOS' or '$(TargetOS)' == 'iOSSimulator' or '$(TargetOS)' == 'MacCatalyst' or '$(TargetOS)' == 'tvOS' or '$(TargetOS)' == 'tvOSSimulator' or '$(TargetOS)' == 'Android' or '$(TargetOS)' == 'Browser' or '$(TargetOS)' == 'wasi'">true</TargetsMobile>
-    <TargetsAppleMobile Condition="'$(TargetOS)' == 'iOS' or '$(TargetOS)' == 'iOSSimulator' or '$(TargetOS)' == 'MacCatalyst' or '$(TargetOS)' == 'tvOS' or '$(TargetOS)' == 'tvOSSimulator'">true</TargetsAppleMobile>
+    <TargetsMobile Condition="'$(TargetOS)' == 'ios' or '$(TargetOS)' == 'iossimulator' or '$(TargetOS)' == 'maccatalyst' or '$(TargetOS)' == 'tvos' or '$(TargetOS)' == 'tvossimulator' or '$(TargetOS)' == 'android' or '$(TargetOS)' == 'browser' or '$(TargetOS)' == 'wasi'">true</TargetsMobile>
+    <TargetsAppleMobile Condition="'$(TargetOS)' == 'ios' or '$(TargetOS)' == 'iossimulator' or '$(TargetOS)' == 'maccatalyst' or '$(TargetOS)' == 'tvos' or '$(TargetOS)' == 'tvossimulator'">true</TargetsAppleMobile>
   </PropertyGroup>
 
   <!-- Platform property is required by RepoLayout.props in Arcade SDK. -->
@@ -35,7 +35,7 @@
     <TargetArchitecture Condition="'$(TargetArchitecture)' == '' and '$(_hostArch)' == 'loongarch64'">loongarch64</TargetArchitecture>
     <TargetArchitecture Condition="'$(TargetArchitecture)' == '' and '$(_hostArch)' == 's390x'">s390x</TargetArchitecture>
     <TargetArchitecture Condition="'$(TargetArchitecture)' == '' and '$(_hostArch)' == 'ppc64le'">ppc64le</TargetArchitecture>
-    <TargetArchitecture Condition="'$(TargetArchitecture)' == '' and ('$(TargetOS)' == 'Browser' or '$(RuntimeIdentifier)' == 'browser-wasm')">wasm</TargetArchitecture>
+    <TargetArchitecture Condition="'$(TargetArchitecture)' == '' and ('$(TargetOS)' == 'browser' or '$(RuntimeIdentifier)' == 'browser-wasm')">wasm</TargetArchitecture>
     <TargetArchitecture Condition="'$(TargetArchitecture)' == '' and ('$(TargetOS)' == 'wasi' or '$(RuntimeIdentifier)' == 'wasi-wasm')">wasm</TargetArchitecture>
     <TargetArchitecture Condition="'$(TargetArchitecture)' == '' and '$(TargetsMobile)' == 'true'">x64</TargetArchitecture>
     <TargetArchitecture Condition="'$(TargetArchitecture)' == ''">x64</TargetArchitecture>
@@ -166,46 +166,46 @@
     <_portableOS>linux</_portableOS>
     <_portableOS Condition="'$(_runtimeOS)' == 'linux-musl'">linux-musl</_portableOS>
     <_portableOS Condition="'$(_runtimeOS)' == 'linux-bionic'">linux-bionic</_portableOS>
-    <_portableOS Condition="'$(_hostOS)' == 'OSX'">osx</_portableOS>
+    <_portableOS Condition="'$(_hostOS)' == 'osx'">osx</_portableOS>
     <_portableOS Condition="'$(_runtimeOS)' == 'win' or '$(TargetOS)' == 'windows'">win</_portableOS>
-    <_portableOS Condition="'$(_runtimeOS)' == 'FreeBSD' or '$(TargetOS)' == 'FreeBSD'">freebsd</_portableOS>
+    <_portableOS Condition="'$(_runtimeOS)' == 'freebsd' or '$(TargetOS)' == 'freebsd'">freebsd</_portableOS>
     <_portableOS Condition="'$(_runtimeOS)' == 'illumos' or '$(TargetOS)' == 'illumos'">illumos</_portableOS>
-    <_portableOS Condition="'$(_runtimeOS)' == 'Solaris' or '$(TargetOS)' == 'Solaris'">solaris</_portableOS>
-    <_portableOS Condition="'$(_runtimeOS)' == 'Browser'">browser</_portableOS>
+    <_portableOS Condition="'$(_runtimeOS)' == 'solaris' or '$(TargetOS)' == 'solaris'">solaris</_portableOS>
+    <_portableOS Condition="'$(_runtimeOS)' == 'browser'">browser</_portableOS>
     <_portableOS Condition="'$(_runtimeOS)' == 'wasi'">wasi</_portableOS>
     <_portableOS Condition="'$(_runtimeOS)' == 'maccatalyst'">maccatalyst</_portableOS>
     <_portableOS Condition="'$(_runtimeOS)' == 'ios'">ios</_portableOS>
-    <_portableOS Condition="'$(_runtimeOS)' == 'iOSSimulator'">iossimulator</_portableOS>
+    <_portableOS Condition="'$(_runtimeOS)' == 'iossimulator'">iossimulator</_portableOS>
     <_portableOS Condition="'$(_runtimeOS)' == 'tvos'">tvos</_portableOS>
-    <_portableOS Condition="'$(_runtimeOS)' == 'tvOSSimulator'">tvossimulator</_portableOS>
+    <_portableOS Condition="'$(_runtimeOS)' == 'tvossimulator'">tvossimulator</_portableOS>
     <_portableOS Condition="'$(_runtimeOS)' == 'android'">android</_portableOS>
 
     <_runtimeOS Condition="$(_runtimeOS.StartsWith('tizen'))">linux</_runtimeOS>
     <_runtimeOS Condition="'$(PortableBuild)' == 'true'">$(_portableOS)</_runtimeOS>
 
     <_packageLibc Condition="$(_runtimeOS.Contains('musl'))">-musl</_packageLibc>
-    <_packageOS Condition="'$(CrossBuild)' == 'true'">$(_hostOS.ToLowerInvariant)$(_packageLibc)</_packageOS>
+    <_packageOS Condition="'$(CrossBuild)' == 'true'">$(_hostOS)$(_packageLibc)</_packageOS>
     <_packageOS Condition="'$(_packageOS)' == '' and '$(PortableBuild)' == 'true'">$(_portableOS)</_packageOS>
     <_packageOS Condition="'$(_packageOS)' == ''">$(_runtimeOS)</_packageOS>
   </PropertyGroup>
 
   <PropertyGroup Label="CalculateRID">
-    <_toolsRID Condition="'$(CrossBuild)' == 'true'">$(_hostOS.ToLowerInvariant)-$(_hostArch)</_toolsRID>
+    <_toolsRID Condition="'$(CrossBuild)' == 'true'">$(_hostOS)-$(_hostArch)</_toolsRID>
     <_toolsRID Condition="'$(BuildingInsideVisualStudio)' == 'true'">$(_runtimeOS)-x64</_toolsRID>
     <_toolsRID Condition="'$(_toolsRID)' == ''">$(_runtimeOS)-$(_hostArch)</_toolsRID>
 
     <!-- There are no WebAssembly tools, so use the default ones -->
-    <_toolsRID Condition="'$(_runtimeOS)' == 'Browser'">linux-x64</_toolsRID>
-    <_toolsRID Condition="'$(_runtimeOS)' == 'Browser' and '$(HostOS)' == 'windows'">win-x64</_toolsRID>
-    <_toolsRID Condition="'$(_runtimeOS)' == 'Browser' and '$(HostOS)' == 'osx'">osx-x64</_toolsRID>
+    <_toolsRID Condition="'$(_runtimeOS)' == 'browser'">linux-x64</_toolsRID>
+    <_toolsRID Condition="'$(_runtimeOS)' == 'browser' and '$(HostOS)' == 'windows'">win-x64</_toolsRID>
+    <_toolsRID Condition="'$(_runtimeOS)' == 'browser' and '$(HostOS)' == 'osx'">osx-x64</_toolsRID>
 
     <!-- There are no Android tools, so use the default ones -->
     <_toolsRID Condition="'$(_runtimeOS)' == 'android' or '$(_runtimeOS)' == 'linux-bionic'">linux-x64</_toolsRID>
     <_toolsRID Condition="('$(_runtimeOS)' == 'android' or '$(_runtimeOS)' == 'linux-bionic') and '$(HostOS)' == 'windows'">win-x64</_toolsRID>
     <_toolsRID Condition="('$(_runtimeOS)' == 'android' or '$(_runtimeOS)' == 'linux-bionic') and '$(HostOS)' == 'osx'">osx-x64</_toolsRID>
 
     <!-- There are no Mac Catalyst, iOS or tvOS tools and it can be built on OSX only, so use that -->
-    <_toolsRID Condition="'$(_runtimeOS)' == 'maccatalyst' or '$(_runtimeOS)' == 'ios' or '$(_runtimeOS)' == 'iOSSimulator' or '$(_runtimeOS)' == 'tvos' or '$(_runtimeOS)' == 'tvOSSimulator'">osx-x64</_toolsRID>
+    <_toolsRID Condition="'$(_runtimeOS)' == 'maccatalyst' or '$(_runtimeOS)' == 'ios' or '$(_runtimeOS)' == 'iossimulator' or '$(_runtimeOS)' == 'tvos' or '$(_runtimeOS)' == 'tvossimulator'">osx-x64</_toolsRID>
 
     <!-- There are no non-portable builds for Ilasm, Ildasm, ILC etc. -->
     <ToolsRID Condition="'$(PortableBuild)' != 'true' and '$(_portableOS)' == 'linux'">linux-$(_hostArch)</ToolsRID>
@@ -220,19 +220,19 @@
   </PropertyGroup>
 
   <PropertyGroup Label="CalculateTargetOSName" Condition="'$(SkipInferTargetOSName)' != 'true'">
-    <TargetsFreeBSD Condition="'$(TargetOS)' == 'FreeBSD'">true</TargetsFreeBSD>
+    <TargetsFreeBSD Condition="'$(TargetOS)' == 'freebsd'">true</TargetsFreeBSD>
     <Targetsillumos Condition="'$(TargetOS)' == 'illumos'">true</Targetsillumos>
-    <TargetsSolaris Condition="'$(TargetOS)' == 'Solaris'">true</TargetsSolaris>
-    <TargetsLinux Condition="'$(TargetOS)' == 'Linux' or '$(TargetOS)' == 'Android'">true</TargetsLinux>
-    <TargetsNetBSD Condition="'$(TargetOS)' == 'NetBSD'">true</TargetsNetBSD>
-    <TargetsOSX Condition="'$(TargetOS)' == 'OSX'">true</TargetsOSX>
-    <TargetsMacCatalyst Condition="'$(TargetOS)' == 'MacCatalyst'">true</TargetsMacCatalyst>
-    <TargetsiOS Condition="'$(TargetOS)' == 'iOS' or '$(TargetOS)' == 'iOSSimulator'">true</TargetsiOS>
-    <TargetstvOS Condition="'$(TargetOS)' == 'tvOS' or '$(TargetOS)' == 'tvOSSimulator'">true</TargetstvOS>
-    <TargetsiOSSimulator Condition="'$(TargetOS)' == 'iOSSimulator'">true</TargetsiOSSimulator>
-    <TargetstvOSSimulator Condition="'$(TargetOS)' == 'tvOSSimulator'">true</TargetstvOSSimulator>
-    <TargetsAndroid Condition="'$(TargetOS)' == 'Android'">true</TargetsAndroid>
-    <TargetsBrowser Condition="'$(TargetOS)' == 'Browser'">true</TargetsBrowser>
+    <TargetsSolaris Condition="'$(TargetOS)' == 'solaris'">true</TargetsSolaris>
+    <TargetsLinux Condition="'$(TargetOS)' == 'linux' or '$(TargetOS)' == 'android'">true</TargetsLinux>
+    <TargetsNetBSD Condition="'$(TargetOS)' == 'netbsd'">true</TargetsNetBSD>
+    <TargetsOSX Condition="'$(TargetOS)' == 'osx'">true</TargetsOSX>
+    <TargetsMacCatalyst Condition="'$(TargetOS)' == 'maccatalyst'">true</TargetsMacCatalyst>
+    <TargetsiOS Condition="'$(TargetOS)' == 'ios' or '$(TargetOS)' == 'iossimulator'">true</TargetsiOS>
+    <TargetstvOS Condition="'$(TargetOS)' == 'tvos' or '$(TargetOS)' == 'tvossimulator'">true</TargetstvOS>
+    <TargetsiOSSimulator Condition="'$(TargetOS)' == 'iossimulator'">true</TargetsiOSSimulator>
+    <TargetstvOSSimulator Condition="'$(TargetOS)' == 'tvossimulator'">true</TargetstvOSSimulator>
+    <TargetsAndroid Condition="'$(TargetOS)' == 'android'">true</TargetsAndroid>
+    <TargetsBrowser Condition="'$(TargetOS)' == 'browser'">true</TargetsBrowser>
     <TargetsWasi Condition="'$(TargetOS)' == 'wasi'">true</TargetsWasi>
     <TargetsWindows Condition="'$(TargetOS)' == 'windows'">true</TargetsWindows>
     <TargetsUnix Condition="'$(TargetsFreeBSD)' == 'true' or '$(Targetsillumos)' == 'true' or '$(TargetsSolaris)' == 'true' or '$(TargetsLinux)' == 'true' or '$(TargetsNetBSD)' == 'true' or '$(TargetsOSX)' == 'true' or '$(TargetsMacCatalyst)' == 'true' or '$(TargetstvOS)' == 'true' or '$(TargetsiOS)' == 'true' or '$(TargetsAndroid)' == 'true'">true</TargetsUnix>

Directory.Build.targets

@@ -1,4 +1,4 @@
-<Project>
+<Project InitialTargets="ValidateTargetOSLowercase">
   <PropertyGroup>
     <!--
     For non-SDK projects that import this file and then import Microsoft.Common.targets,
@@ -78,6 +78,11 @@
     <Description>$(PackageDescription)</Description>
   </PropertyGroup>
 
+  <Target Name="ValidateTargetOSLowercase"
+          Condition="!$(TargetOS.Equals($(TargetOS.ToLower()), StringComparison.InvariantCulture))">
+    <Error Text="The passed-in TargetOS property value '$(TargetOS)' must be lowercase." />
+  </Target>
+
   <ItemDefinitionGroup>
     <TargetPathWithTargetPlatformMoniker>
       <IsReferenceAssemblyProject>$(IsReferenceAssemblyProject)</IsReferenceAssemblyProject>

docs/coding-guidelines/interop-guidelines.md

@@ -126,10 +126,10 @@ internal static partial class Interop // contents of Common\src\Interop\Windows\
 ```
 
 ### Build System
-When building dotnet/runtime, we use the "TargetOS" property to control what target platform we are building for. The valid values for this property are windows (which is the default value from MSBuild when running on Windows), Linux and OSX.
+When building dotnet/runtime, we use the "TargetOS" property to control what target platform we are building for. The valid values for this property are windows (which is the default value from MSBuild when running on Windows), linux and osx.
 
 #### Project Files
-Whenever possible, a single .csproj should be used per assembly, spanning all target platforms, e.g. System.Console.csproj includes conditional entries for when targeting Windows vs when targeting Linux. A property can be passed to dotnet build to control which flavor is built, e.g. `dotnet build /p:TargetOS=OSX System.Console.csproj`.
+Whenever possible, a single .csproj should be used per assembly, spanning all target platforms, e.g. System.Console.csproj includes conditional entries for when targeting Windows vs when targeting Linux. A property can be passed to dotnet build to control which flavor is built, e.g. `dotnet build /p:TargetOS=osx System.Console.csproj`.
 
 ### Constants
 - Wherever possible, constants should be defined as "const". Only if the data type doesn't support this (e.g. IntPtr) should they instead be static readonly fields.

docs/coding-guidelines/project-guidelines.md

@@ -19,15 +19,15 @@ Below is a list of all the various options we pivot the project builds on:
 
 - **Target Frameworks:** .NETFramework, .NETStandard, .NETCoreApp
 - **Platform Runtimes:** .NETFramework (aka CLR/Desktop), CoreCLR, Mono
-- **OS:** windows, Linux, OSX, FreeBSD, AnyOS
+- **OS:** windows, linux, osx, freebsd, AnyOS
 - **Flavor:** Debug, Release
 
 ## Individual build properties
 The following are the properties associated with each build pivot
 
 - `$(BuildTargetFramework) -> Any .NETCoreApp or .NETFramework TFM, e.g. net8.0`
-- `$(TargetOS) -> Windows | Linux | OSX | FreeBSD | [defaults to running OS when empty]`
-- `$(Configuration) -> Release | [defaults to Debug when empty]`
+- `$(TargetOS) -> windows | linux | osx | freebsd | ... | [defaults to running OS when empty]`
+- `$(Configuration) -> Debug | Release | [defaults to Debug when empty]`
 - `$(TargetArchitecture) - x86 | x64 | arm | arm64 | [defaults to x64 when empty]`
 - `$(RuntimeOS) - win7 | osx10.10 | ubuntu.14.04 | [any other RID OS+version] | [defaults to running OS when empty]` See [RIDs](https://github.com/dotnet/runtime/tree/main/src/libraries/Microsoft.NETCore.Platforms) for more info.
 

docs/workflow/building/coreclr/cross-building.md

@@ -92,7 +92,7 @@ Very similarly to generating the _ROOTFS_, cross-building for FreeBSD follows th
 
 ```bash
 export ROOTFS_DIR=/path/to/runtime/.tools/rootfs/x64
-./build.sh --subset clr --configuration Release --cross --os FreeBSD
+./build.sh --subset clr --configuration Release --cross --os freebsd
 ```
 
 #### Cross-Compiling CoreCLR for other VFP Configurations
@@ -130,12 +130,12 @@ However, you might find yourself needing to (re)build them because either you ma
 ./src/coreclr/build-runtime.sh -arm64 -hostarch x64 -component crosscomponents -cmakeargs "-DCLR_CROSS_COMPONENTS_BUILD=1"
 ```
 
-The output of running this command is placed in `artifacts/bin/coreclr/Linux.<target_arch>.<configuration>/<host_arch>`. For our example, it would be `artifacts/bin/coreclr/Linux.arm64.Release/x64`.
+The output of running this command is placed in `artifacts/bin/coreclr/linux.<target_arch>.<configuration>/<host_arch>`. For our example, it would be `artifacts/bin/coreclr/linux.arm64.Release/x64`.
 
 On Windows, you can build these cross-targeting diagnostic libraries with the `linuxdac` and `alpinedac` subsets from the root `build.cmd` script. That said, you can also use the `build-runtime.cmd` script, like with Linux. These builds also require you to pass the `-os` flag to specify the target OS. For example:
 
 ```cmd
-.\src\coreclr\build-runtime.cmd -arm64 -hostarch x64 -os Linux -component crosscomponents -cmakeargs "-DCLR_CROSS_COMPONENTS_BUILD=1"
+.\src\coreclr\build-runtime.cmd -arm64 -hostarch x64 -os linux -component crosscomponents -cmakeargs "-DCLR_CROSS_COMPONENTS_BUILD=1"
 ```
 
 If you're building the cross-components in powershell, you'll need to wrap `"-DCLR_CROSS_COMPONENTS_BUILD=1"` with single quotes (`'`) to ensure things are escaped correctly for CMD.
@@ -159,5 +159,5 @@ docker run --rm -v <RUNTIME_REPO_PATH>:/runtime -w /runtime -e ROOTFS_DIR=/cross
 Using Docker to cross-build for FreeBSD is very similar to any other Docker Linux build. You only need to use the appropriate image and pass `--os` as well to specify this is not an architecture(-only) build. For example, to make a FreeBSD x64 build:
 
 ```bash
-docker run --rm -v <RUNTIME_REPO_PATH>:/runtime -w /runtime -e ROOTFS_DIR=/crossrootfs/x64 mcr.microsoft.com/dotnet-buildtools/prereqs:ubuntu-18.04-cross-freebsd-12-20220831130538-f13d79e ./build.sh --subset clr --cross --os FreeBSD
+docker run --rm -v <RUNTIME_REPO_PATH>:/runtime -w /runtime -e ROOTFS_DIR=/crossrootfs/x64 mcr.microsoft.com/dotnet-buildtools/prereqs:ubuntu-18.04-cross-freebsd-12-20220831130538-f13d79e ./build.sh --subset clr --cross --os freebsd
 ```

docs/workflow/building/coreclr/linux-instructions.md

@@ -76,7 +76,7 @@ To build CoreCLR on Linux, run `build.sh` while specifying the `clr` subset:
 ./build.sh --subset clr <other args>
 ```
 
-After the build is completed, there should be some files placed in `artifacts/bin/coreclr/Linux.<arch>.<configuration>` (for example `artifacts/bin/coreclr/Linux.x64.Release`). The most important binaries are the following:
+After the build is completed, there should be some files placed in `artifacts/bin/coreclr/linux.<arch>.<configuration>` (for example `artifacts/bin/coreclr/linux.x64.Release`). The most important binaries are the following:
 
 * `corerun`: The command line host.  This program loads and starts the CoreCLR runtime and passes the managed program (e.g. `program.dll`) you want to run with it.
 * `libcoreclr.so`: The CoreCLR runtime itself.

docs/workflow/building/coreclr/macos-instructions.md

@@ -19,7 +19,7 @@ To build CoreCLR on macOS, run `build.sh` while specifying the `clr` subset:
 ./build.sh --subset clr <other args>
 ```
 
-After the build has completed, there should be some files placed in `artifacts/bin/coreclr/OSX.<arch>.<configuration>` (for example `artifacts/bin/coreclr/OSX.x64.Release`). The most important binaries are the following:
+After the build has completed, there should be some files placed in `artifacts/bin/coreclr/osx.<arch>.<configuration>` (for example `artifacts/bin/coreclr/osx.x64.Release`). The most important binaries are the following:
 
 * `corerun`: The command line host. This program loads and starts the CoreCLR runtime and passes the managed program (e.g. `program.dll`) you want to run with it.
 * `libcoreclr.dylib`: The CoreCLR runtime itself.