If you ever get error messages like this (Sierra can bey any MacOS version name):

  • Error: Xcode alone is not sufficient on Sierra.
  • Xcode alone is not sufficient on Sierra.

Then run this on the terminal:

xcode-select --install 

This works even if it is already installed, as the message will also show up when the current install is outdated.

Note from [Wayback] `xcode-select –install` required for OS X 10.9 Xcode command-line tools (like `zlib-devel`) « The Wiert Corner – irregular stream of stuff

There is one catch though: it might fail as you first have to start Xcode once and accept the license agreement.

--jeroen

Via my answer on [Wayback] ruby - Error Message "Xcode alone is not sufficient on Sierra" - Stack Overflow