[WebAssemlby] MC: Don't write COMDAT symbols as global imports

This was causing undefined references at link time in lld.

Differential Revision: https://reviews.llvm.org/D41959

llvm-svn: 322309
diff --git a/llvm/lib/MC/MCContext.cpp b/llvm/lib/MC/MCContext.cpp
index ac2e454..c7c6ca7 100644
--- a/llvm/lib/MC/MCContext.cpp
+++ b/llvm/lib/MC/MCContext.cpp
@@ -490,8 +490,10 @@
                                          const Twine &Group, unsigned UniqueID,
                                          const char *BeginSymName) {
   MCSymbolWasm *GroupSym = nullptr;
-  if (!Group.isTriviallyEmpty() && !Group.str().empty())
+  if (!Group.isTriviallyEmpty() && !Group.str().empty()) {
     GroupSym = cast<MCSymbolWasm>(getOrCreateSymbol(Group));
+    GroupSym->setComdat(true);
+  }
 
   return getWasmSection(Section, K, GroupSym, UniqueID, BeginSymName);
 }