This extends the use of this attribute on ARM and AArch64 from SVN r325900 (where it was only checked for fixed stack allocations on ARM/AArch64, but for all stack allocations on X86). This also adds a testcase for the existing use of disabling the fixed stack probe with the attribute on ARM and AArch64. Differential Revision: https://reviews.llvm.org/D44291 llvm-svn: 327897