Don't pass x86-only options on non-x86 targets in c-c++-common/fcf-protection-[67].c (PR testsuite/84243)

	PR testsuite/84243
	* c-c++-common/fcf-protection-6.c: Only pass -mshstk on x86
	targets.
	* c-c++-common/fcf-protection-7.c: Likewise for -mibt.

From-SVN: r257432