libmemunreachable: turn off MEM_ALOGV messages

The move to async safe logging in I3d3b2111f6f6bf8a0d7039295d34d5168c191651
caused MEM_ALOGV messages to print even when NDEBUG was set.

Test: builds
Change-Id: Ibebe69d8c96f8f2556991c1eb5446a77782d43c7
diff --git a/log.h b/log.h
index 0f1bb8a..44c5f85 100644
--- a/log.h
+++ b/log.h
@@ -26,7 +26,18 @@
 #define MEM_ALOGE(...) async_safe_format_log(ANDROID_LOG_ERROR, LOG_TAG, ##__VA_ARGS__)
 #define MEM_ALOGW(...) async_safe_format_log(ANDROID_LOG_WARN, LOG_TAG, ##__VA_ARGS__)
 #define MEM_ALOGI(...) async_safe_format_log(ANDROID_LOG_INFO, LOG_TAG, ##__VA_ARGS__)
-#define MEM_ALOGV(...) async_safe_format_log(ANDROID_LOG_VERBOSE, LOG_TAG, ##__VA_ARGS__)
+#define MEM_ALOGV_IMPL(...) async_safe_format_log(ANDROID_LOG_VERBOSE, LOG_TAG, ##__VA_ARGS__)
+
+#ifdef NDEBUG
+#define MEM_ALOGV(...)             \
+  do {                             \
+    if (0) {                       \
+      MEM_ALOGV_IMPL(__VA_ARGS__); \
+    }                              \
+  } while (0)
+#else
+#define MEM_ALOGV(...) MEM_ALOGV_IMPL(__VA_ARGS__)
+#endif
 
 #define MEM_LOG_ALWAYS_FATAL(...) async_safe_fatal(__VA_ARGS__)