Initialize BSSSection explicitly in InitMachOMCObjectFileInfo() to appease msvc.

This can revert r191087.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@191128 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/MC/MCObjectFileInfo.cpp b/lib/MC/MCObjectFileInfo.cpp
index c620e8c..958648c 100644
--- a/lib/MC/MCObjectFileInfo.cpp
+++ b/lib/MC/MCObjectFileInfo.cpp
@@ -39,6 +39,9 @@
     = Ctx->getMachOSection("__DATA", "__data", 0,
                            SectionKind::getDataRel());
 
+  // BSSSection might not be expected initialized on msvc.
+  BSSSection = 0;
+
   TLSDataSection // .tdata
     = Ctx->getMachOSection("__DATA", "__thread_data",
                            MCSectionMachO::S_THREAD_LOCAL_REGULAR,