#80154 followups:

• __TestBuildMode: crossgen2 (as in git grep __TestBuildMode.*crossgen2) should use helix so we can revert 2324602 (i.e. use published crossgen2.exe instead of dotnet crossgen2.dll)

• Crossgen2Tool (as in git grep '<Crossgen2Tool' should similarly use published crossgen2.exe instead of crossgen2.dll and while working on it, we should deduplicate

    runtime/src/tasks/Crossgen2Tasks/PrepareForReadyToRunCompilation.cs
    runtime/src/tasks/Crossgen2Tasks/ResolveReadyToRunCompilers.cs
    runtime/src/tasks/Crossgen2Tasks/RunReadyToRunCompiler.cs
  

  and

    sdk/src/Tasks/Microsoft.NET.Build.Tasks/PrepareForReadyToRunCompilation.cs
    sdk/src/Tasks/Microsoft.NET.Build.Tasks/ResolveReadyToRunCompilers.cs
    sdk/src/Tasks/Microsoft.NET.Build.Tasks/RunReadyToRunCompiler.cs
  

• Remove apphost.exe requirement from crossgen2_publish; some ResolveFrameworkRef.. type of target make it mandatory during the publish. It will allow us to delete this two-step workaround

  runtime/src/tests/Common/Directory.Build.targets

  Lines 59 to 64 in 62835af

  	<MakeDir Condition="'$(Crossgen2Supported)' == 'true'" Directories="$(ArtifactsObjDir)coreclr\crossgen2_publish\$(TargetOS).$(TargetArchitecture).$(RuntimeConfiguration)" />
  	<Copy
  	SourceFiles="$(_apphostPath)"
  	DestinationFiles="$(ArtifactsObjDir)coreclr\crossgen2_publish\$(TargetOS).$(TargetArchitecture).$(RuntimeConfiguration)\apphost$(ExeSuffix)"
  	Condition="'$(Crossgen2Supported)' == 'true'" />

• Integrate src/tests/build.sh/cmd with top-level build.sh/cmd, so when we use build.sh -c release -rc checked, the corresponding test command is src/tests/build.sh -release -p:RuntimeConfiguration=checked instead of what we have now src/tests/build.sh -checked -p:LibrariesConfiguration=release. This will allow us to remove workaround like

  runtime/src/tests/Common/Directory.Build.targets

  Lines 40 to 57 in 62835af

  	<!-- Copy apphost to crossgen2_publish directory.
  	The default configuration between product and tests are flipped. When we build project like:
  	`build -c debug -rc checked`, the corresponding test command is `src/tests/build -checked -p:LibrariesConfiguration=debug`,
  	instead of `-debug -p:RuntimeConfiguration=checked`. That forces us to either pass the
  	`HostConfiguration=debug` explicitly or fix this disparity; both of which will break the dev workflow.
  	As a workaround, we will first check if the directory pointed by `HostConfiguration` exists, then check
  	`LibrariesConfiguration`.
  	-->
  	<PropertyGroup Condition="'$(Crossgen2Supported)' == 'true'">
  	<_targetOS>$(TargetOS)</_targetOS>
  	<_targetOS Condition="'$(_targetOS)' == 'windows'">win</_targetOS>
  	<_apphostPath Condition="Exists('$(ArtifactsBinDir)$(_targetOS)-$(TargetArchitecture).$(HostConfiguration)\corehost\apphost$(ExeSuffix)')">$(ArtifactsBinDir)$(_targetOS)-$(TargetArchitecture).$(HostConfiguration)\corehost\apphost$(ExeSuffix)</_apphostPath>
  	<_apphostPath Condition="'$(_apphostPath)' == '' and Exists('$(ArtifactsBinDir)$(_targetOS)-$(TargetArchitecture).$(LibrariesConfiguration)\corehost\apphost$(ExeSuffix)')">$(ArtifactsBinDir)$(_targetOS)-$(TargetArchitecture).$(LibrariesConfiguration)\corehost\apphost$(ExeSuffix)</_apphostPath>
  	<_toolsConfiguration Condition="Exists('$(ArtifactsBinDir)ILLink.Tasks\$(ToolsConfiguration)\$(NetCoreAppToolCurrent)\ILLink.Tasks.dll')">$(ToolsConfiguration)</_toolsConfiguration>
  	<_toolsConfiguration Condition="Exists('$(ArtifactsBinDir)ILLink.Tasks\$(LibrariesConfiguration)\$(NetCoreAppToolCurrent)\ILLink.Tasks.dll')">$(LibrariesConfiguration)</_toolsConfiguration>
  	</PropertyGroup>