Otherwise, users will be stuck running an old copy of guix and the guix-daemon
if they copy the service files instead of symlinking them.
* etc/guix-daemon.conf.in, etc/guix-daemon.service.in, etc/guix-publish.conf.in,
etc/guix-publish.service.in: Expand @localstatedir@ instead of @bindir@.
* nix/local.mk (etc/guix-%.service, etc/guix-%.conf): Use @localstatedir@
instead of @bindir@.