Adding two --with-* configure options for the systemd pkgconfig-defined
variables gives opportunity for distcheck to succeed; the variables use
hardcoded paths to /usr/lib/systemd/... without a PREFIX, so the paths
need to be relocated to $dc_install_base, a variable distcheck uses for
the normal variables that begin with PREFIX.
systemd pkgconfig module is already required, which will have system
paths defined as pkg-config variables. This simplifies autofoo, and
installs tmpfile.d into a system location under /usr, rather than
admin location under /etc.
Ikey Doherty