Newly introduced systemd detection does not work

[bertptrs]

In 8df0c1f the detection of systemd-based systems was changed to seeing whether the program systemd can be found. However, on most systems, this program is not actually part of systemd, at least not on ArchLinux. It now incorrectly assumes there is no init system, where there clearly is.

A more appropriate check (if you don't want to return to the old behaviour) is to do the same check for the systemctl binary. That one is unique to systemd systems (at least as far as I know) and should always be on the path.

[roehling]

The old check failed on my Ubuntu 18.04 LTS system, so I implemented your suggestion. Thank you for the bug report!