BQ: Conditionally compile validateConsistencyLocked

- Only enable it on userdebug and eng builds so that it won't slow
  down user builds.

Change-Id: I70933a23d54657fdf5cbc23873da4fbee84b9a26
diff --git a/libs/gui/Android.mk b/libs/gui/Android.mk
index 8a965dd..635020e 100644
--- a/libs/gui/Android.mk
+++ b/libs/gui/Android.mk
@@ -36,6 +36,8 @@
 # Don't warn about struct padding
 LOCAL_CPPFLAGS += -Wno-padded
 
+LOCAL_CPPFLAGS += -DDEBUG_ONLY_CODE=$(if $(filter userdebug eng,$(TARGET_BUILD_VARIANT)),1,0)
+
 LOCAL_SRC_FILES := \
 	IGraphicBufferConsumer.cpp \
 	IConsumerListener.cpp \