The __atomic_test_and_set and __atomic_clear code was correct.
They needed locking.
Replaced to code with assembly code.
The changes are in include/stdatomic.h, lib/stdatomic.c, lib/atomic.S
Enabled tests/tests2/124_atomic_counter.c for apple again.
Also moved lib/fetch_and_add.S code to lib/atomic.S.
Removed lib/fetch_and_add.S
Adjusted lib/Makefile