Build F# repo with .Net 6.0 because, F# Interactive built in main is still net5.0

[dsyme]

When running F# Interactive it can't load a .NET 6 DLL. because fsi.exe is still .NET 5.0

@brettfo This was the error I mentioned to you on teams. Here the script is doing #r on a .NET 6 DLL.

This isn't a repro but an example of the kind of problem we get:

>\GitHub\dsyme\fsharp\artifacts\bin\fsi\Debug\net5.0\fsi.exe --legacyemit train.fsx --model cnn
System.TypeLoadException: Could not load type 'System.IO.DirectoryInfo' from assembly 'System.Runtime, Version=5.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'.
   at Helpers.Utils.createDir(String dir)
   at <StartupCode$FSI_0003>.$FSI_0003.main@()
Stopped due to error

[dsyme]

It looks like this is only the case for the fsi.exe we build in main. I've checked the release branches and they seem to also build net5.0, however when you run dotnet fsi from the .NET SDK it chooses an fsi.dll which runs .NET 6.0 bits

[KevinRansom]

The shipped SDK always contain fsi and fsc that are built to match the sdk shipped the build of the runtime contained in that specific SDK. So the released bits will always be correct, however, the repo is always going to lag a bit, especially since previews of dotnet 7. are pretty soon going to be released.

I will chat with Brett and see if there is something interesting we can do that makes this less of a problem

[KevinRansom]

now builds net6.0: #12769