Try different compiler versions for OS X CI tests.
Try different compiler versions for OS X CI tests.

clang-15 doesn't work, boost is failing to build with "error: builtin __has_nothrow_assign is deprecated; use __is_nothrow_assignable instead [-Werror,-Wdeprecated-builtins]".

clang-8 works on Mac OS 12 but not in Mac OS 10 and 11. Switching to clang-9 in those.

gcc doesn't work on Mac OS 13 ATM due to https://github.com/iains/gcc-12-branch/issues/6, so I disabled it there (relying on the CI tests with Mac OS 12 instead).

google/fruit,google/fruit,google/fruit