testsuite: Use sync_long_long instead of sync_int_long for atomic-29.c test

testsuite: Use sync_long_long instead of sync_int_long for atomic-29.c test

As discussed, the test tests atomics on doubles which are 64-bit and so we
should use sync_long_long effective target instead of sync_int_long that
covers 64-bit atomics only on 64-bit arches.  I've added -march=pentium
to follow what is documented for sync_long_long, I guess -march=zarch should
be added for s390* too, but haven't tested that.

And using sync_long_long found a syntax error in that effective target
implementation, so I've fixed that too.

2021-09-14  Jakub Jelinek  <jakub@redhat.com>

	* c-c++-common/gomp/atomic-29.c: Add -march=pentium
	dg-additional-options for ia32.  Use sync_long_long effective target
	instead of sync_int_long.
	* lib/target-supports.exp (check_effective_target_sync_long_long): Fix
	a syntax error.