Enable OmniSharp.Cake tests for .NET 6

[bjorkstromm]

No description provided.

[JoeRobich]

🎉

[333fred]

Looks like there are some test failures.

[filipw]

looks like some of the tests deadlocked (?)

[JoeRobich]

This error in the failing MacOS leg looks suspicious.

[fail]: OmniSharp.WorkspaceInitializer
         The project system 'OmniSharp.Cake.CakeProjectSystem' threw exception during initialization.
 System.ComponentModel.Win32Exception (8): An error occurred trying to start process '/Users/runner/work/omnisharp-roslyn/omnisharp-roslyn/test-assets/test-projects/CakeProject/tools/Cake.Bakery.0.9.0/tools/Cake.Bakery.exe' with working directory '/Users/runner/work/omnisharp-roslyn/omnisharp-roslyn/test-assets/test-projects/CakeProject'. Exec format error

[bjorkstromm]

This error in the failing MacOS leg looks suspicious.

[fail]: OmniSharp.WorkspaceInitializer
         The project system 'OmniSharp.Cake.CakeProjectSystem' threw exception during initialization.
 System.ComponentModel.Win32Exception (8): An error occurred trying to start process '/Users/runner/work/omnisharp-roslyn/omnisharp-roslyn/test-assets/test-projects/CakeProject/tools/Cake.Bakery.0.9.0/tools/Cake.Bakery.exe' with working directory '/Users/runner/work/omnisharp-roslyn/omnisharp-roslyn/test-assets/test-projects/CakeProject'. Exec format error

Hmm, we don't have Mono at all in the .NET 6 tests I assume. Cake.Bakery itself is a .NET 6 console app, but it includes a wrapper for Mono. I'll add a check if we are running Mono or .NET6 and launch the appropriate executable based on runtime.

[filipw]

I merged this, although I hope this deadlock is now really gone and not that the checks just passed 'accidentally' 😅