Require an x86 registered target for this test by splitting it out

This is a shot in the dark to fix the hexagon bot, so I'm not 100% sure
this is the issue.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@212871 91177308-0d34-0410-b5e6-96231b3b80d8