add mechanism for configuring system image builds (#54387)

This adds the option to pass a filename of configuration settings when
building the Core/compiler system image (from
`base/compiler/compiler.jl`). This makes it easier to build different
flavors of images, for example it can replace the hack that
PackageCompiler uses to edit the list of included stdlibs, and makes it
easy to change knobs you might want like max_methods.

base/Base.jl

@@ -265,8 +265,28 @@ function strcat(x::String, y::String)
     end
     return out
 end
-include(strcat((length(Core.ARGS)>=2 ? Core.ARGS[2] : ""), "build_h.jl"))     # include($BUILDROOT/base/build_h.jl)
-include(strcat((length(Core.ARGS)>=2 ? Core.ARGS[2] : ""), "version_git.jl")) # include($BUILDROOT/base/version_git.jl)
+
+BUILDROOT::String = ""
+
+baremodule BuildSettings
+end
+
+let i = 1
+    global BUILDROOT
+    while i <= length(Core.ARGS)
+        if Core.ARGS[i] == "--buildsettings"
+            include(BuildSettings, ARGS[i+1])
+            i += 1
+        else
+            BUILDROOT = Core.ARGS[i]
+        end
+        i += 1
+    end
+end
+
+include(strcat(BUILDROOT, "build_h.jl"))     # include($BUILDROOT/base/build_h.jl)
+include(strcat(BUILDROOT, "version_git.jl")) # include($BUILDROOT/base/version_git.jl)
+
 # Initialize DL_LOAD_PATH as early as possible.  We are defining things here in
 # a slightly more verbose fashion than usual, because we're running so early.
 const DL_LOAD_PATH = String[]
@@ -562,7 +582,7 @@ include(mapexpr::Function, mod::Module, _path::AbstractString) = _include(mapexp
 
 # External libraries vendored into Base
 Core.println("JuliaSyntax/src/JuliaSyntax.jl")
-include(@__MODULE__, string((length(Core.ARGS)>=2 ? Core.ARGS[2] : ""), "JuliaSyntax/src/JuliaSyntax.jl")) # include($BUILDROOT/base/JuliaSyntax/JuliaSyntax.jl)
+include(@__MODULE__, string(BUILDROOT, "JuliaSyntax/src/JuliaSyntax.jl")) # include($BUILDROOT/base/JuliaSyntax/JuliaSyntax.jl)
 
 end_base_include = time_ns()
 

base/compiler/compiler.jl

@@ -180,6 +180,18 @@ something(x::Any, y...) = x
 # compiler #
 ############
 
+baremodule BuildSettings
+using Core: ARGS, include
+using Core.Compiler: >, getindex, length
+
+MAX_METHODS::Int = 3
+UNOPTIMIZE_THROW_BLOCKS::Bool = true
+
+if length(ARGS) > 2 && ARGS[2] === "--buildsettings"
+    include(BuildSettings, ARGS[3])
+end
+end
+
 if false
     import Base: Base, @show
 else

base/compiler/types.jl

@@ -206,14 +206,14 @@ struct InferenceParams
 end
 function InferenceParams(
     params::InferenceParams = InferenceParams( # default constructor
-        #=max_methods::Int=# 3,
+        #=max_methods::Int=# BuildSettings.MAX_METHODS,
         #=max_union_splitting::Int=# 4,
         #=max_apply_union_enum::Int=# 8,
         #=max_tuple_splat::Int=# 32,
         #=tuple_complexity_limit_depth::Int=# 3,
         #=ipo_constant_propagation::Bool=# true,
         #=aggressive_constant_propagation::Bool=# false,
-        #=unoptimize_throw_blocks::Bool=# true,
+        #=unoptimize_throw_blocks::Bool=# BuildSettings.UNOPTIMIZE_THROW_BLOCKS,
         #=assume_bindings_static::Bool=# false,
         #=ignore_recursion_hardlimit::Bool=# false);
     max_methods::Int = params.max_methods,

base/cpuid.jl

@@ -21,7 +21,7 @@ Base.:<=(a::ISA, b::ISA) = a.features <= b.features
 Base.:<(a::ISA,  b::ISA) = a.features <  b.features
 Base.isless(a::ISA,  b::ISA) = a < b
 
-include(string(length(Core.ARGS) >= 2 ? Core.ARGS[2] : "", "features_h.jl"))  # include($BUILDROOT/base/features_h.jl)
+include(string(Base.BUILDROOT, "features_h.jl"))  # include($BUILDROOT/base/features_h.jl)
 
 # Keep in sync with `arch_march_isa_mapping`.
 const ISAs_by_family = Dict(

base/filesystem.jl

@@ -159,7 +159,7 @@ uv_fs_req_cleanup(req) = ccall(:uv_fs_req_cleanup, Cvoid, (Ptr{Cvoid},), req)
 include("path.jl")
 include("stat.jl")
 include("file.jl")
-include(string(length(Core.ARGS) >= 2 ? Core.ARGS[2] : "", "file_constants.jl"))  # include($BUILDROOT/base/file_constants.jl)
+include(string(Base.BUILDROOT, "file_constants.jl"))  # include($BUILDROOT/base/file_constants.jl)
 
 ## Operations with File (fd) objects ##
 

base/libc.jl

@@ -17,7 +17,7 @@ if Sys.iswindows()
     export GetLastError, FormatMessage
 end
 
-include(string(length(Core.ARGS) >= 2 ? Core.ARGS[2] : "", "errno_h.jl"))  # include($BUILDROOT/base/errno_h.jl)
+include(string(Base.BUILDROOT, "errno_h.jl"))  # include($BUILDROOT/base/errno_h.jl)
 
 ## RawFD ##
 

base/libuv.jl

@@ -2,7 +2,7 @@
 
 # Core definitions for interacting with the libuv library from Julia
 
-include(string(length(Core.ARGS) >= 2 ? Core.ARGS[2] : "", "uv_constants.jl"))  # include($BUILDROOT/base/uv_constants.jl)
+include(string(Base.BUILDROOT, "uv_constants.jl"))  # include($BUILDROOT/base/uv_constants.jl)
 
 # convert UV handle data to julia object, checking for null
 function uv_sizeof_handle(handle)

base/pcre.jl

@@ -7,7 +7,7 @@ module PCRE
 import ..RefValue
 
 # include($BUILDROOT/base/pcre_h.jl)
-include(string(length(Core.ARGS) >= 2 ? Core.ARGS[2] : "", "pcre_h.jl"))
+include(string(Base.BUILDROOT, "pcre_h.jl"))
 
 const PCRE_LIB = "libpcre2-8"
 

base/sysimg.jl

@@ -68,22 +68,29 @@ let
 
     # Stdlibs sorted in dependency, then alphabetical, order by contrib/print_sorted_stdlibs.jl
     # Run with the `--exclude-jlls` option to filter out all JLL packages
-    stdlibs = [
-        # No dependencies
-        :FileWatching, # used by loading.jl -- implicit assumption that init runs
-        :Libdl, # Transitive through LinAlg
-        :Artifacts, # Transitive through LinAlg
-        :SHA, # transitive through Random
-        :Sockets, # used by stream.jl
-
-        # Transitive through LingAlg
-        # OpenBLAS_jll
-        # libblastrampoline_jll
-
-        # 1-depth packages
-        :LinearAlgebra, # Commits type-piracy and GEMM
-        :Random, # Can't be removed due to rand being exported by Base
-    ]
+    if isdefined(Base.BuildSettings, :INCLUDE_STDLIBS)
+        # e.g. INCLUDE_STDLIBS = "FileWatching,Libdl,Artifacts,SHA,Sockets,LinearAlgebra,Random"
+        stdlibs = Symbol.(split(Base.BuildSettings.INCLUDE_STDLIBS, ","))
+    else
+        # TODO: this is included for compatibility with PackageCompiler, which looks for it.
+        # This should eventually be removed so we only use `BuildSettings`.
+        stdlibs = [
+            # No dependencies
+            :FileWatching, # used by loading.jl -- implicit assumption that init runs
+            :Libdl, # Transitive through LinAlg
+            :Artifacts, # Transitive through LinAlg
+            :SHA, # transitive through Random
+            :Sockets, # used by stream.jl
+
+            # Transitive through LingAlg
+            # OpenBLAS_jll
+            # libblastrampoline_jll
+
+            # 1-depth packages
+            :LinearAlgebra, # Commits type-piracy and GEMM
+            :Random, # Can't be removed due to rand being exported by Base
+        ]
+    end
     # PackageCompiler can filter out stdlibs so it can be empty
     maxlen = maximum(textwidth.(string.(stdlibs)); init=0)
 
@@ -139,6 +146,7 @@ end
 
 empty!(Base.TOML_CACHE.d)
 Base.TOML.reinit!(Base.TOML_CACHE.p, "")
+@eval Base BUILDROOT = ""
 @eval Sys begin
     BINDIR = ""
     STDLIB = ""