In systemd 209, they deprecated -lsystemd-daemon in favor of
-lsystemd. So we'd better actually look at the pkg-config output,
or we'll get warnings on newer distributions.
For some as-yet-unknown-to-me reason, setting CFLAGS so early makes
it so -O2 -g doesn't get added to it later. So, adding it myself
later. Perhaps a better fix here can be found.
Fixes 14072; bugfix on 0.2.6.2-alpha. Based on a patch from h.venev
