Add asm calls to prevent variables from being optimized out

Change-Id: Idcbdaf19f3f15a07b9facaaa8fc5b2ed35bae8fb
diff --git a/aos/realtime.cc b/aos/realtime.cc
index 9f7e810..6668855 100644
--- a/aos/realtime.cc
+++ b/aos/realtime.cc
@@ -92,10 +92,12 @@
   uint8_t data[4096 * 8];
   // Not 0 because linux might optimize that to a 0-filled page.
   memset(data, 1, sizeof(data));
+  __asm__ __volatile__("" :: "m" (data));
 
   static const size_t kHeapPreallocSize = 512 * 1024;
   char *const heap_data = static_cast<char *>(malloc(kHeapPreallocSize));
   memset(heap_data, 1, kHeapPreallocSize);
+  __asm__ __volatile__("" :: "m" (heap_data));
   free(heap_data);
 }