re PR testsuite/51258 (64-bit gcc.dg/atomic-compare-exchange-5.c link failure on 32-bit Solaris/x86)

	PR testsuite/51258
	* lib/target-supports.exp
	(check_effective_target_sync_long_long): Also supported on 32bit
	x86 targets.  Add comment about required dg-options.
	Add alpha*-*-* targets.
	(check_effective_target_sync_long_long_runtime): Ditto.

	* gcc.dg/atomic-op-4.c (dg-options): Add -march=pentium for
	32bit x86 targets.
	* gcc.dg/atomic-compare-exchange-4.c: Ditto.
	* gcc.dg/atomic-exchange-4.c: Ditto.
	* gcc.dg/atomic-load-4.c: Ditto.
	* gcc.dg/atomic-store-4.c: Ditto.
	* gcc.dg/di-longlong64-sync-1.c: Ditto.
	* gcc.dg/di-sync-multithread.c: Ditto.
	* gcc.dg/simulate-thread/atomic-load-longlong.c: Ditto.
	* gcc.dg/simulate-thread/atomic-other-longlong.c: Ditto.

From-SVN: r181728