MC: duplicate .file test for WoA (SVN r207341)

Since the COFF tests are dependent on X86, duplicate the test for ARM.  Use the
default check prefix.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207365 91177308-0d34-0410-b5e6-96231b3b80d8