Suppress unused return values when using -c opt.

Change-Id: I9cfe54f1b71d4b2b5e321cd09282db2852664377
diff --git a/aos/linux_code/ipc_lib/queue.cc b/aos/linux_code/ipc_lib/queue.cc
index 81ad51b..21a2ea8 100644
--- a/aos/linux_code/ipc_lib/queue.cc
+++ b/aos/linux_code/ipc_lib/queue.cc
@@ -1,4 +1,5 @@
 #if !AOS_DEBUG
+#undef NDEBUG
 #define NDEBUG
 #endif