llvm/test/DebugInfo/dwarf-public-names.ll: Mark it as XFAIL for PECOFF targets, for now. Investigating.

FIXME: llvm-dwarfdump doesn't handle PECOFF.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@190374 91177308-0d34-0410-b5e6-96231b3b80d8