Currently systemd FTBFS on the buildds. Looking at the failure, this seems to
be because the kernel running on the buildds (4.9.12-titan-p1+) does not have
CONFIG_USER_NS enabled. This was enabled back in 2013 for src:linux, but this
seems to be a custom-compiled kernel which presumably hasn't had its config
updated. I suggest you do so unless you have good reason not to. Also, is there
a reason why src:linux isn't building the CONFIG_TITAN (SMP and non-SMP)
versions, which would avoid this in future?