Detect if `xcode-select` was executed properly

[mrexodia]

On my machine I had xcode installed, but still had the command line tools selected. This causes the build to fail when configuring LLVM. If it is a requirement to have xcode installed and selected it would be good to detect that up front and inform the user how to fix the problem.

Vanilla LLVM is building for me without issues with just the command line tool though, so not sure why there is an error in your port.

[ekilmer]

Hmmm. Do you have any of the error messages? I haven't heard of anyone else running into this.

There was some recent weirdness in the past months with an XCode update that was causing command-line tool issues, but if you are able to build vanilla LLVM, then I'm not sure how the vcpkg port is much different.

[ekilmer]

Also, do you know how to check whether xcode-select was executed properly?

[mrexodia]

I’ll try to reproduce it later, would have to unselect xcode somehow to try…

[ekilmer]

No worries. Homebrew does some detection somehow, so I might look there.