Bug#792187: systemd: systemctl start not working when ReadWriteDirectories is a symlink

[nfb]

> Are you suspecting the arm architecture or the custom kernel to be the
> culprit? Can you test the stock Debian kernel on arm?
> Your custom kernel, does it have every option enabled as specified in
> /usr/share/doc/systemd/README.gz

Yes i suspect about the kernel, also because among the error logs i
reported we can read:

kernel: Chromium OS LSM: Mount path with symlinks prohibited

I've not built the kernel by myself, so i don't know much details
about it, but it's the default chromeOS kernel shipped with this arm
chromebook. There is no way to try the stock debian kernel due to how
the boot process works on this device (restricted boot loader and
separate signed kernel partition).