ARM: Support SingleParameterDotFile on WoA

Currently, the integrated assembler is the only choice for assembling Windows on
ARM binaries.  IAS supports the .file <filename> directive which emits the file
symbol into the resulting object binary.  Mark the GNU COFF information to
indicate support for this feature.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207341 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/ARM/MCTargetDesc/ARMMCAsmInfo.cpp

@@ -89,6 +89,7 @@ void ARMCOFFMCAsmInfoGNU::anchor() { }
 
 ARMCOFFMCAsmInfoGNU::ARMCOFFMCAsmInfoGNU() {
   AlignmentIsInBytes = false;
+  HasSingleParameterDotFile = true;
 
   CommentString = "@";
   Code16Directive = ".code\t16";