Fix __has_builtin() issue on macOS
Fix __has_builtin() issue on macOS

macOS incorrectly always defines __has_builtin(). This causes issues with GCC which does not support  __has_builtin() yet.

See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90835

kimwalisch/primecount,kimwalisch/primecount,kimwalisch/primecount