[x86] Give this test a bare metal triple so it doesn't use the weird
Darwin x86 asm comment prefix designed to work around GAS on that
platform. That makes the comment-matching of the test much more stable.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214629 91177308-0d34-0410-b5e6-96231b3b80d8