[WebAssembly] LTO: Honor comdat groups when loading bitcode files

But don't apply comdat groups when loading the LTO object files.
This is basically the same logic used by the ELF linker.

Differential Revision: https://reviews.llvm.org/D61924

llvm-svn: 360782
diff --git a/lld/wasm/SymbolTable.cpp b/lld/wasm/SymbolTable.cpp
index 2099616..1a16b63 100644
--- a/lld/wasm/SymbolTable.cpp
+++ b/lld/wasm/SymbolTable.cpp
@@ -59,7 +59,7 @@
 
   for (StringRef Filename : LTO->compile()) {
     auto *Obj = make<ObjFile>(MemoryBufferRef(Filename, "lto.tmp"), "");
-    Obj->parse();
+    Obj->parse(true);
     ObjectFiles.push_back(Obj);
   }
 }
@@ -476,7 +476,7 @@
 }
 
 bool SymbolTable::addComdat(StringRef Name) {
-  return Comdats.insert(CachedHashStringRef(Name)).second;
+  return ComdatGroups.insert(CachedHashStringRef(Name)).second;
 }
 
 // The new signature doesn't match.  Create a variant to the symbol with the