c-family: Yet another fix for _BitInt & __sync_* builtins [PR117641]

c-family: Yet another fix for _BitInt & __sync_* builtins [PR117641]

Sorry, the last patch only partially fixed the __sync_* ICEs with
_BitInt(128) on ia32.
Even for !fetch we need to error out and return 0.  I was afraid of
APIs like __atomic_exchange/__atomic_compare_exchange, those obviously
need to be supported even on _BitInt(128) on ia32, but they actually never
sync_resolve_size, they are handled by adding the size argument and using
the library version much earlier.
For fetch && !orig_format (i.e. __atomic_fetch_* etc.) we need to return -1
so that we handle it with a manualy __atomic_load +
__atomic_compare_exchange loop in the caller, all other cases should
be rejected.

2024-11-22  Jakub Jelinek  <jakub@redhat.com>

	PR c/117641
	* c-common.cc (sync_resolve_size): For size 16 with _BitInt
	on targets where TImode isn't supported, use goto incompatible if
	!fetch.

	* gcc.dg/bitint-117.c: New test.

(cherry picked from commit 44984f7f7523f136085ba60fd107ba8309d4115b)