[3.11] gh-99337: Fix compile errors with gcc 12 on macOS (GH-99470) (#99638)

gh-99337: Fix compile errors with gcc 12 on macOS (GH-99470)

Fix a number of compile errors with GCC-12 on macOS:

1. In pylifecycle.c the compile rejects _Pragma within a declaration
2. posixmodule.c was missing a number of ..._RUNTIME macros for non-clang on macOS
3. _ctypes assumed that __builtin_available is always present on macOS
(cherry picked from commit cdde29dde90947df9bac39c1d19479914fb3db09)

Co-authored-by: Ronald Oussoren <ronaldoussoren@mac.com>

Co-authored-by: Ronald Oussoren <ronaldoussoren@mac.com>