MacOS CI newly fails

[michael-schwarz]

The CI for MacOS now fails with

  # Detecting depexts using vars: arch=arm64, os=macos, os-distribution=homebrew, os-family=homebrew
  [ERROR] No solution for goblint:   * Missing dependency:
              - goblint
              unmet availability conditions, e.g. 'os-distribution != "alpine" & arch != "arm64"'

  Command failed: opam --cli=2.1 list --readonly --with-test --external '--resolve=goblint' returned 20

Maybe Github switched the default instance to arm64?

[sim642]

Fixed by 9c785b129aea4338a0d0258bd6bb88b14a331397.