meson: install README.logs independently of HAVE_SYSV_COMPAT

meson: install README.logs independently of HAVE_SYSV_COMPAT

That file provides compatiblity (or more precisely the explanation for the lack
of compatibility) with syslog daemons. Those are used quite independently of
sysvinit. For example, RHEL uses rsyslog with systemd. We create
/var/log/journal, so it's no biggie to also provide /var/log/README with the
explanation. Let's keep it, since it might help some confused users, even when
compat with sysvinit is gone.