Variable/Conditional USE_SYSTEMD_DAEMON is not being set properly.
The Autotool is generating an inconsistent Makefile, where it does
not remove the Type=notify and NotifyAccess=all bits from the
systemd unit file (xdm.service.in).
The reason is that it tries to auto identify if the libsystemd is
present in the system, thus setting its default value to auto.
Resulting in the AM_CONDITIONAL at the line always evaluating to true.
(xauto != xno)
Because the systemd unit file has the Type=notify, Systemd keeps
killing the XDM service due to timeout. The timeout occurs because it
never notifies systemd with a call to sd_notify.
I've created a patch that fixes it. I couldn't create a fork here so
I am submitting it here, let me know what am I missing to create a fork
and create a proper `Merge request.