C#: Keep only one framework reference nuget package in standalone

[tamasvajk]

No description provided.

[tamasvajk]

The DCA analysis shows compilation error increases in:

• luciana-pereira/fhir-server - this seems to be transient, see https://github.com/github/codeql-csharp-team/issues/397
• OpenKH/OpenKh - this seems to be a valid issue. This repo targets netstandard2.0, net6.0, net472. There's a 22% increase in compilation errors.
• akkadotnet/akka.net, 5% increase

  [001] Found .NET Core/Framework DLLs in NuGet packages at /tmp/GitHub/packages/43e4457282c3f9fa/microsoft.netcore.app.ref. Not adding installation directory.
  [001] Removed reference /tmp/GitHub/packages/43e4457282c3f9fa/microsoft.netframework.referenceassemblies.net471/1.0.3
  [001] Removed reference /tmp/GitHub/packages/43e4457282c3f9fa/netstandard.library/2.0.3/lib/netstandard1.0

• NLog/NLog, 9% increase.

  [001] Found .NET Core/Framework DLLs in NuGet packages at /tmp/GitHub/packages/43e4457282c3f9fa/microsoft.netcore.app.ref. Not adding installation directory.
  [001] Removed reference /tmp/GitHub/packages/43e4457282c3f9fa/microsoft.netframework.referenceassemblies.net472/1.0.3
  [001] Removed reference /tmp/GitHub/packages/43e4457282c3f9fa/netstandard.library/2.0.3/lib/netstandard1.0

[michaelnebel]

Excellent! 👍

Yes, so this happens exactly when different target frameworks are used in different project files (if it was in the same file the assets logic would "catch" this and only use one)?