ubuntu base 16.04 core armhf enable systemctl/systemd/dev ttyAMA0

1. buildroot/lfs 可以不使用systemd, 2. Ubuntu/Debian 依赖systemd . 内核编译需要CONFIG_FHANDLE Refer to https://github.com/systemd/systemd/blob/master/README REQUIREMENTS: Linux kernel >= 3.13 Linux kernel >= 4.2 for unified cgroup hierarchy support Kernel Config Options: C