gh-133261: Increase C stack margin

[vstinner]

Fix a random crash in test_frame.test_repr_deep() on x86-64.

• Issue: test_frame does crash randomly on Linux (x86-64, ppc64le, s390x) #133261

[vstinner]

@markshannon: Does it look reasonable to you?

[markshannon]

Rather than increasing the multiple of PYOS_STACK_MARGIN_BYTES that we use, I think it would be better to increase PYOS_STACK_MARGIN_BYTES itself.
PYOS_STACK_MARGIN_BYTES should the safe margin between the soft limit and the hard limit and between the hard limit and the real hardware limit.

We already increased it for Windows debug builds, so let's increase it for non-debug and linux builds to match.
Change #define PYOS_LOG2_STACK_MARGIN 11 to #define PYOS_LOG2_STACK_MARGIN 12.

[vstinner]

Change #define PYOS_LOG2_STACK_MARGIN 11 to #define PYOS_LOG2_STACK_MARGIN 12.

It doesn't work: test_frame still crash. I increased PYOS_LOG2_STACK_MARGIN up to 14, it does still crash.

You should be able to reproduce to reproduce the crash on Linux using a release build. Just run test_frame a few times and you get a crash.

[vstinner]

Without this change, test_frame does crash after a few attempts.

With this change, it does no longer crash:

$ ./python -u -m test -j2 -F test_frame 
...
0:01:00 load avg: 3.31 [ 65] test_frame passed
0:01:00 load avg: 3.31 [ 66] test_frame passed
^C

[vstinner]

This change is not needed.