As previously announced, execute order 66: https://lists.freedesktop.org/archives/systemd-devel/2022-September/048352.html The meson options split-usr, rootlibdir and rootprefix become no-ops that print a warning if they are set to anything other than the default values. We can remove them in a future release.
This change is only about the source tree. We have tmpfiles.d/, modprobe.d/, sysctl.d/, and sysusers.d/, but for historical reasons, rules/ didn't fit this pattern. We also *install* it as rules.d/. Let's rename to be consistent.