ASP.NET's global.json `tool\vs` section behaves poorly

[ericstj]

I was running into a situation where I my ASP.NET build was consistently failing to find FSharp targets when building.

https://github.com/dotnet/aspnetcore/blob/9a6b2eb7ee0eaffcdd3a361b06899b4fe735a4d6/global.json#L16-L22

I found the root cause was my devbox (VS Client SKU) had VC, ATL, x64 and ARM64 tools. I was missing ARM64 ATL libs - apparently wasn't part of the workflows installed.

The result was that ASPNETCore build decided to not use my installed VS, but instead decided to download the Xcopy-MSBuild package, which not only was missing all the VC components but also missing FSharp targets 🙃

Seems this isn't working as expected....