GitLab

Supported from GCC 8 and up, and Compiler Explorer suggests it works as
expected with Clang since 3.6 (2014).

- Fixes situation where building embedded MicroPython with -O0 and
  MICROPY_NLR_X64 crashes at runtime (due to nlr_push pushing the
  frame pointer register EBP). Closes #12421.

- Allows removing the macOS tweak to undo pushing EBP onto the stack
  in the generated function prelude.
Signed-off-by: Angus Gratton <angus@redyak.com.au>