[inline asm] Add a test case for r180873. Test case needs to be on the clang
side because we need an inline asm diagnostics handler in place.  Unfortunately,
we emit a .s file because we need to build the SelectionDAG to hit the backend
issue.
rdar://13446483



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@180874 91177308-0d34-0410-b5e6-96231b3b80d8