[llvm-ml] Restore VK_WEAKREF special case to fix alias.asm

Author: MaskRay

llvm/lib/MC/MCExpr.cpp

@@ -478,7 +478,13 @@ static bool canExpand(const MCSymbol &Sym, bool InSet) {
   if (Sym.isWeakExternal())
     return false;
 
-  Sym.getVariableValue(true);
+  const MCExpr *Expr = Sym.getVariableValue(true);
+  // Special case for llvm-ml alias
+  const auto *Inner = dyn_cast<MCSymbolRefExpr>(Expr);
+  if (Inner) {
+    if (Inner->getKind() == MCSymbolRefExpr::VK_WEAKREF)
+      return false;
+  }
 
   if (InSet)
     return true;