CoreRT does not support net5.0-windows TFM

[Suchiman]

Trying to use that TFM results in

C:\Program Files\dotnet\sdk\5.0.100-preview.8.20417.9\Sdks\Microsoft.NET.Sdk\targets\Microsoft.PackageDependencyResolution.targets(180,5): error NETSDK1047: Assets file '...\obj\project.assets.json' doesn't have a target for 'net5.0/win-x64'. Ensure that restore has run and that you have included 'net5.0' in the TargetFrameworks for your project. You may also need to include 'win-x64' in your project's RuntimeIdentifiers.

during
dotnet publish -c Release -r win-x64

[RalfKornmannEnvision]

Not sure if this is related but CoreRT is still a little bit behind the runtime. I noticed this when I needed to compile my own RyuJIT for cross compile and needed the nuget with an ARM64/Unix BCL. The Preview 8 version did not work because of at least one breaking change.