Error `The C compiler identification is unknown`.

[treeform]

If you get errors such as this:

• The C compiler identification is unknown
• xcode-select: error: tool 'xcodebuild' requires Xcode, but active developer directory '/Library/Developer/CommandLineTools' is a command line tools instance

And you have xcode installed, you need to switch to non-command line xcode:

sudo xcode-select -s /Applications/Xcode.app/Contents/Developer

It would be nice of CMake script would tell you that.