参考rpi-buildroot通过软链接方式添加外部buildroot包

https://github.com/cellux/rpi-buildroot.git

# create symlinks for board-specific scripts and add-on packages

for p in board/rpi package/rpi; do

 ln -s $(readlink -f ../rpi-buildroot/$p) $p

done

# override packages which have been customized

for p in luajit; do

 rm -rf package/$p

 ln -s $(readlink -f ../rpi-buildroot/package/$p) package/$p

done

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post-build.sh 中 ${1} 为rootfs target目录

可引用Makefile中的变量，如${BASE_DIR}即为 Makefile中的$(BASE_DIR)