[HLSL] Restore code lost in merge commit

Code in handleInitPriorityAttr() to emit an HLSL specific diagnostic was lost
in the merge. This change restores that lost code.

Author: tahonermann

clang/lib/Sema/SemaDeclAttr.cpp

@@ -4955,6 +4955,11 @@ static void handleInitPriorityAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
     return;
   }
 
+  if (S.getLangOpts().HLSL) {
+    S.Diag(AL.getLoc(), diag::err_hlsl_init_priority_unsupported);
+    return;
+  }
+
   if (S.getCurFunctionOrMethodDecl()) {
     S.Diag(AL.getLoc(), diag::err_init_priority_object_attr);
     AL.setInvalid();