The reason is most likely that you haven't agreed to the Xcode terms. Please open Xcode once or run sudo xcrun clang
from a Terminal.
If you have already agreed to the terms another reason could be that xcode-select
isn't pointing to the correct path. Run xcode-select -print-path
in a Terminal to view the current path. Use sudo xcode-select -switch <path>
to change the path pointed to.
The next version of RoboVM (0.0.6) will show more helpful error messages when these problems occur.