Android.mk中C++使用

参考：

https://gerrit.twrp.me/c/android_bootable_recovery/+/4366/1/Android.mk

ifeq ($(BOARD_USES_RECOVERY_AS_BOOT), true)
    LOCAL_CFLAGS += -DBOARD_USES_RECOVERY_AS_BOOT
endif
ifeq ($(BOARD_BUILD_SYSTEM_ROOT_IMAGE), true)
    LOCAL_CFLAGS += -DBOARD_BUILD_SYSTEM_ROOT_IMAGE
endif

#if defined BOARD_USES_RECOVERY_AS_BOOT && defined BOARD_BUILD_SYSTEM_ROOT_IMAGE
    mConst.SetValue("tw_uses_initramfs", "1");
#else
    mConst.SetValue("tw_uses_initramfs", "0");
#endif