[PATCH] Support installing systemd unit file.

[Julien Cristau]

On Sun, Aug 28, 2011 at 17:12:41 -0400, Gaetan Nadon wrote:

> In essence, when the user input clearly indicates he wants to set
> systemdsystemunitdir, an error should occur if systemd is not installed.
> 
Err, I don't think that makes sense.  I should be able to build xdm
without systemd installed, even if I want to run it with systemd at a
later point or on another host.

Cheers,
Julien