unittest: Disable MachineInstrClone.CopyCallSiteInfo on Windows

A bot error (http://45.33.8.238/win/12463/step_11.txt) reports 'unknown
file: error: SEH exception with code 0x3221225477 thrown in the test
body', but I don't know what causes this.

It looks like this has come up before, but afaict the root causes could
be different:

  https://reviews.llvm.org/rL329195, and in
  http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20180910/587425.html

I tried testing locally with UBSan, but that didn't uncover anything.

Author: vedantk

llvm/unittests/CodeGen/MachineInstrTest.cpp

@@ -383,6 +383,9 @@ TEST(MachineInstrExtraInfo, RemoveExtraInfo) {
   ASSERT_FALSE(MI->getHeapAllocMarker());
 }
 
+#ifndef _WIN32
+// See discussion on https://reviews.llvm.org/D77685, this is throwing a SEH
+// exception when run on a Windows bot despite being UBSan-clean.
 TEST(MachineInstrClone, CopyCallSiteInfo) {
   LLVMContext Ctx;
   Module Mod("Module", Ctx);
@@ -402,6 +405,7 @@ TEST(MachineInstrClone, CopyCallSiteInfo) {
   MF->CloneMachineInstrBundle(*MBB, MBB->end(), *MI);
   EXPECT_EQ(MF->getCallSitesInfo().size(), 2u);
 }
+#endif
 
 static_assert(is_trivially_copyable<MCOperand>::value, "trivially copyable");