fix warning

src/drivers/driver_common/driver_common.c

@@ -67,7 +67,7 @@ void _starpu_driver_end_job(struct starpu_worker_s *args, starpu_job_t j, struct
 	int starpu_top=starpu_top_status_get();
 	int workerid = args->workerid;
 	unsigned calibrate_model = 0;
-	enum starpu_perf_archtype archtype = args->perf_arch;
+	enum starpu_perf_archtype archtype STARPU_ATTRIBUTE_UNUSED = args->perf_arch;
 
 	STARPU_TRACE_END_CODELET_BODY(j, archtype);