Comment (by Roland Haas):

This is fixed in the instructions provided in the tutorial notebook. In a nutshell, clang is not (has never been) supported.Instead one must install either macports or homebrew and use the actual gcc compiler in there. Please see this email: http://lists.einsteintoolkit.org/pipermail/users/2022-March/008436.html

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Ticket URL: https://bitbucket.org/einsteintoolkit/tickets/issues/2604/simbuilding-problem-on-macos-monterey