Diagnose importing non-ossa module when -enable-ossa-modules is on

Author: meg-gupta

lib/Serialization/SerializedModuleLoader.cpp

@@ -1244,7 +1244,8 @@ void swift::serialization::diagnoseSerializedASTLoadFailure(
                        moduleBufferID);
     break;
   case serialization::Status::NotInOSSA:
-    if (Ctx.SerializationOpts.ExplicitModuleBuild) {
+    if (Ctx.SerializationOpts.ExplicitModuleBuild ||
+        Ctx.SILOpts.EnableOSSAModules) {
       Ctx.Diags.diagnose(diagLoc,
                          diag::serialization_non_ossa_module_incompatible,
                          ModuleName);