Make sure the user doesn't introduce duplicate worker order values

src/core/jobs.c

@@ -500,6 +500,7 @@ int _starpu_push_local_task(struct _starpu_worker *worker, struct starpu_task *t
 
 	if (task->execute_on_a_specific_worker && task->workerorder)
 	{
+		STARPU_ASSERT_MSG(task->workerorder >= worker->current_ordered_task_order, "worker order values must not have duplicates");
 		/* Put it in the ordered task ring */
 		unsigned needed = task->workerorder - worker->current_ordered_task_order + 1;
 		if (worker->local_ordered_tasks_size < needed)