- add .gnu.warning.SYMBOL support to ld.lld(1)

Index: tools/lld/ELF/SymbolTable.cpp
--- tools/lld/ELF/SymbolTable.cpp.orig
+++ tools/lld/ELF/SymbolTable.cpp
@@ -90,6 +90,7 @@ Symbol *SymbolTable::insert(StringRef name) {
   sym->canInline = true;
   sym->referenced = false;
   sym->traced = false;
+  sym->gwarn = false;
   sym->scriptDefined = false;
   sym->partition = 1;
   return sym;