Use framework provided by the SDK

[MichalStrehovsky]

The ILCompiler NuGet package currently includes a copy of all the inbox framework assemblies:

runtime/src/installer/pkg/projects/Microsoft.DotNet.ILCompiler/Microsoft.DotNet.ILCompiler.pkgproj

Line 14 in b4e258a

<File Include="@(LibrariesRuntimeFiles)" TargetPath="framework" />

The .targets embedded in the ILCompiler package then replace the framework implementation assemblies that the SDK knows about with this private copy:

runtime/src/coreclr/nativeaot/BuildIntegration/Microsoft.NETCore.Native.targets

Lines 117 to 118 in 87777b6

	<DefaultFrameworkAssemblies Include="@(FrameworkAssemblies)" />
	<DefaultFrameworkAssemblies Include="@(PrivateSdkAssemblies)" />

runtime/src/coreclr/nativeaot/BuildIntegration/Microsoft.NETCore.Native.targets

Lines 158 to 159 in 87777b6

	<DefaultFrameworkAssemblies Include="@(FrameworkAssemblies)" />
	<DefaultFrameworkAssemblies Include="@(PrivateSdkAssemblies)" />

We do this because up until the move of NativeAOT to the runtime repo, we had customizations in the framework libraries that were not present in the shipping framework assemblies, and the NativeAOT CoreLib didn't version with the libraries that are in the SDK either (the latter is still true for users who consume NativeAOT as a NuGet package vs those that will consume it from the SDK - we sometimes do things like moving types from framework assemblies to CoreLib and such changes are not compatible with old frameworks).

The NativeAOT integration provided by the SDK should probably not be shipping a separate copy of these.

I'm putting this into .NET 7 milestone for consideration, but I'm not sure how much it's needed and how much it's nice to have.

Cc @agocke @LakshanF

[jkotas]

we sometimes do things like moving types from framework assemblies to CoreLib and such changes are not compatible with old frameworks

These types of changes are still happening today.

In order to do this, we would need to guarantee that the runtime pack version and NativeAOT package version are the same.

[MichalStrehovsky]

dotnet/performance#2905 ran into us replacing the framework with our versions - it's not possible to use new Collections.Immutable with 7.0 NativeAOT because we replace it with the old version.

[MichalStrehovsky]

Closing in favor of #87060.