Make MC use Windows COFF on Windows and add tests.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@109494 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/X86/X86TargetMachine.cpp b/lib/Target/X86/X86TargetMachine.cpp
index 900b516..0552a8e 100644
--- a/lib/Target/X86/X86TargetMachine.cpp
+++ b/lib/Target/X86/X86TargetMachine.cpp
@@ -46,6 +46,8 @@
                                     bool RelaxAll) {
   Triple TheTriple(TT);
   switch (TheTriple.getOS()) {
+  case Triple::Win32:
+    return createWinCOFFStreamer(Ctx, TAB, *_Emitter, _OS);
   default:
     return createMachOStreamer(Ctx, TAB, _OS, _Emitter, RelaxAll);
   }