This is an alternative way of D139627 suggested by Craig. Creently only X86 backend uses this attribute. Let's just emit for X86 only.
Reviewed By: craig.topper
Differential Revision: https://reviews.llvm.org/D139701
When generating __clang_call_terminate use SetLLVMFunctionAttributes
to set the default function attributes, like we do for all the other
functions generated by clang. This fixes a problem where target
features from the command line weren't being applied to this function.
Differential Revision: https://reviews.llvm.org/D138679