Runtime async tests not building as runtime async

[jakobbotsch]

To repro:

1. Delete ./src/tests/async/Directory.Build.targets
2. Build a test, e.g. .\dotnet.cmd build .\src\tests\async\small\small.csproj -c Release /p:BuildAsStandalone=true
3. Inspect the output .dll and notice that it is compiled as async1

cc @agocke @VSadov

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[tannergooding]

@jakobbotsch does it work if you define /p:RoslynCompilerType=Custom?

This might have been broken by #117975 which removed the toolset override for the tests, which was necessary to get some shipping APIs into .NET 10 RC1.

The toolset override shouldn't be needed anymore since runtime-async was merged into main for dotnet/roslyn. However, it's possible we still need to specify its a custom compiler type for the feature to activate.

[jakobbotsch]

@jakobbotsch does it work if you define /p:RoslynCompilerType=Custom?

No, that didn't seem to help. But returning the stuff removed from src/tests/Directory.Build.props in that PR does make it work again.

[tannergooding]

Looks like we've not had backflow from dotnet/dotnet to main in a week and so we never ended up actually picking up the updated Roslyn bits.

I'm following up on this.

[agocke]

@tannergooding where are we with this? Can we manually update the Roslyn ref in the meantime?

[tannergooding]

where are we with this? Can we manually update the Roslyn ref in the meantime?

@agocke Code flow in general has been blocked for nearly 2 weeks since no unified build has succeeded.

We could try to update the Roslyn ref manually, but that might mess with code flow even more and so I'd defer to @ViktorHofer and @mmitche on that.

[tannergooding]

We're expecting a successful build later today after dotnet/dotnet#2230 goes in.