在下载完RK3399 Linux SDK后的第一次编译时，报以下错误：
you need to install 'unbuffer' (from package expect or expect-dev)
log saved on /home/user5/rk3399/br.log
tail: cannot open '/home/user5/rk3399/br.log' for reading: No such file or directory
Command exited with non-zero status 1
you take 0:01.47 to build builroot
====Build buildroot failed!====
解决办法：
命令行输入： unbuffer
会得到以下提示：sudo apt install expect
直接在命令行输入提示内容即可。
