Add support for dotnet and xplat

[dfederm]

Today this feature only works in Windows with a Visual Studio install and with the x64 flavor of MSBuild. Notably, dotnet is not supported.

Really this feature would need to go into MSBuild, and perhaps even all the way into BuildXL, but tracking it here since it'll likely be driven from here.

[klemmchr]

It's quite sad to see that this only supports msbuild. I was hoping to use this with dotnet. Is there any progress on this?

[dfederm]

No, no progress on this.