Explicitly reference Roslyn compiler toolset version that will ship i…

…n preview 7

- see also dotnet/efcore#16370 and dotnet/efcore#16385 discussions
- grab latest from the '.NET Core 3 Release' channel

Directory.Build.targets

@@ -125,6 +125,11 @@
       <TargetingPackVersion Condition="'%(TargetFramework)' == 'netstandard2.1' and '$(IsServicingBuild)' != 'true'">$(NETStandardLibraryRefPackageVersion)</TargetingPackVersion>
     </KnownFrameworkReference>
 
+    <!-- Track compiler separately from Arcade.-->
+    <PackageReference Include="Microsoft.Net.Compilers.Toolset"
+        Version="$(MicrosoftNetCompilersToolsetVersion)"
+        PrivateAssets="all"
+        IsImplicitlyDefined="true" />
   </ItemGroup>
 
   <PropertyGroup Condition=" '$(CopySymbolsToArtifacts)' == 'true' AND '$(TargetFramework)' != '' ">

eng/Version.Details.xml

@@ -420,5 +420,9 @@
       <Uri>https://github.com/aspnet/Extensions</Uri>
       <Sha>531db4e313e577192cdbca3931c4298b6db1e611</Sha>
     </Dependency>
+    <Dependency Name="Microsoft.Net.Compilers.Toolset" Version="3.3.0-beta1-19351-01">
+      <Uri>https://github.com/dotnet/roslyn</Uri>
+      <Sha>c91adff42c488aef2c2c532a7b053fb55e0c16ea</Sha>
+    </Dependency>
   </ToolsetDependencies>
 </Dependencies>

eng/Versions.props

@@ -33,8 +33,6 @@
   <PropertyGroup Label="Arcade settings">
     <!-- Opt-in to Arcade tools for building VSIX projects. -->
     <UsingToolVSSDK>true</UsingToolVSSDK>
-    <!-- Opt-in to using the version of the Roslyn compiler bundled with Arcade. -->
-    <UsingToolMicrosoftNetCompilers Condition="'$(MSBuildProjectExtension)' == '.csproj' or '$(MSBuildProjectExtension)' == '.fsproj' or '$(MSBuildProjectExtension)' == '.vbproj'">true</UsingToolMicrosoftNetCompilers>
     <!-- Only use Microsoft.NETFramework.ReferenceAssemblies on non-windows builds. Using this on Windows breaks MVC runtime compilation. -->
     <UsingToolNetFrameworkReferenceAssemblies Condition="'$(OS)' != 'Windows_NT'">true</UsingToolNetFrameworkReferenceAssemblies>
     <!-- Disable XLIFF tasks -->
@@ -53,6 +51,8 @@
   <PropertyGroup Label="Automated">
     <!-- Packages from dotnet/arcade -->
     <MicrosoftDotNetGenAPIPackageVersion>1.0.0-beta.19323.4</MicrosoftDotNetGenAPIPackageVersion>
+    <!-- Packages from dotnet/roslyn -->
+    <MicrosoftNetCompilersToolsetVersion>3.3.0-beta1-19351-01</MicrosoftNetCompilersToolsetVersion>
     <!-- Packages from dotnet/core-setup -->
     <MicrosoftExtensionsDependencyModelPackageVersion>3.0.0-preview7-27826-20</MicrosoftExtensionsDependencyModelPackageVersion>
     <MicrosoftNETCoreAppRefPackageVersion>3.0.0-preview7-27826-20</MicrosoftNETCoreAppRefPackageVersion>
@@ -255,6 +255,10 @@
       https://dotnetfeed.blob.core.windows.net/dotnet-core/index.json;
       https://grpc.jfrog.io/grpc/api/nuget/v3/grpc-nuget-dev;
     </RestoreSources>
+    <RestoreSources Condition="'$(DotNetBuildOffline)' != 'true' AND $(MicrosoftNetCompilersToolsetVersion.Contains('-')) ">
+      $(RestoreSources);
+      https://dotnet.myget.org/F/roslyn/api/v3/index.json;
+    </RestoreSources>
     <!-- TODO remove this once we move Microsoft.Internal.AspNetCore.H2Spec.All to a non-myget feed -->
     <RestoreSources>
       $(RestoreSources);