added CFG_EXAMPLE_MSC_READONLY to NuTuny-SDK-NUC120 board.mk

hw/bsp/nutiny_sdk_nuc120/board.mk

@@ -3,6 +3,7 @@ CFLAGS += \
   -mthumb \
   -mabi=aapcs-linux \
   -mcpu=cortex-m0 \
+  -DCFG_EXAMPLE_MSC_READONLY \
   -DCFG_TUSB_MCU=OPT_MCU_NUC120
 
 # All source paths should be relative to the top level.