[Sema,X86] Add explicit check to ensure that builtins that require x86-64...

[Sema,X86] Add explicit check to ensure that builtins that require x86-64 target throw an error if used on 32-bit target.

If these builtins are allowed to go through on a 32-bit target they will fire assertions in the backend.

Fixes PR28635.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@276250 91177308-0d34-0410-b5e6-96231b3b80d8