-CFLAGS = -c $(INCLUDE) -Wall -Werror -pedantic -std=gnu99 $(APP_CFLAGS)
-#CFLAGS = -c $(INCLUDE) -pedantic -std=gnu99 $(APP_CFLAGS)
+# compile hint: -flto to minimise size.
+CFLAGS = -c $(INCLUDE) -Wall -Werror -fdata-sections -ffunction-sections -pedantic -std=c99 -Os $(APP_CFLAGS)
+#CFLAGS = -c $(INCLUDE) -Wall -Werror -pedantic -std=c99 -Os $(APP_CFLAGS)