Consider replacing CoreCompileCache with Roslyn DeterministicKey

[rainersigwald]

Roslyn is considering exposing an API to compute a key that describes the inputs to a compilation (dotnet/roslyn#57162).

That could be used to replace the CoreCompileCache concept in Common.targets:

msbuild/src/Tasks/Microsoft.Common.CurrentVersion.targets

Lines 3643 to 3673 in 7434b57

	<!--
	============================================================
	_GenerateCompileDependencyCache
	Generate a file used to track compiler dependencies between incremental build
	executions. This handles cases where items are added or removed from a glob (e.g.
	<Compile Include="**\*.cs" />) and can't otherwise be detected with timestamp
	comparisons. The file contains a hash of compiler inputs that are known to
	contribute to incremental build inconsistencies.
	============================================================
	-->
	<Target Name="_GenerateCompileDependencyCache" Condition="'$(DesignTimeBuild)' != 'true' and '$(BuildingProject)' == 'true'" DependsOnTargets="ResolveAssemblyReferences">
	<ItemGroup>
	<CustomAdditionalCompileInputs Include="$(IntermediateOutputPath)$(MSBuildProjectFile).CoreCompileInputs.cache" />
	<CoreCompileCache Include="@(Compile)" />
	<CoreCompileCache Include="@(ReferencePath)" />
	<CoreCompileCache Include="$(DefineConstants)" />
	</ItemGroup>
	<Hash
	ItemsToHash="@(CoreCompileCache)"
	IgnoreCase="$([MSBuild]::ValueOrDefault(`$(CoreCompileCacheIgnoreCase)`, `true`))">
	<Output TaskParameter="HashResult" PropertyName="CoreCompileDependencyHash" />
	</Hash>
	<WriteLinesToFile Lines="$(CoreCompileDependencyHash)" File="$(IntermediateOutputPath)$(MSBuildProjectFile).CoreCompileInputs.cache" Overwrite="True" WriteOnlyWhenDifferent="True" />
	<ItemGroup>
	<FileWrites Include="$(IntermediateOutputPath)$(MSBuildProjectFile).CoreCompileInputs.cache" />
	</ItemGroup>
	</Target>

That was introduced to avoid problems with the Compile list changing between runs (#1328).

However, if Roslyn exposed a task with similar API to the Csc/Vbc tasks that returned (something like) the DeterministicKey instead of doing compilation, we could use that output instead (instead of having to follow the CoreCompile inputs as in #5334).

This came up when @RikkiGibson and I were talking about some stuff.

[RikkiGibson]

cc @jaredpar

[jaredpar]

This seems like a good use case for the API. Calculating this key though does require us to effectively read in all of the files that will be used in a compilation event: source files, references, etc ... The key is content based hence it needs the values.

Given we'd likely do this work in the server that probably won't add a ton of cost. Many of the values are already cached there but do want to make sure we're clear that is part of the operation here.