When using the "add_systemd_unit" initpcio function, the systemd unit is added to the initramfs. However if that unit has an override defined in /etc/systemd/system, that override isn't correctly carried over.
The code for add_systemd_unit is in /usr/lib/initcpio/install/systemd. That file also have an "add_systemd_drop_in" which isn't used, but can be used to implement this.

The bug was discovered after trying to add a service (pcscd - smart card daemon) to boot. Normally it would depend on "sockets.target" and systemd won't start it during launch. Adding an override with "defaultdependencies=no" and a new "RequiredBy" would let the service start, but it isn't copied to initramfs.

A fix can be made by simply checking the /etc/ directory on call to "add_systemd_unit"

Steps to reproduce:
1. Override a service by "systemctl edit xxx.service"
2. Call "add_systemd_unit xxx.service" in an initcpio hook
3. Browse lsinitcpio and confirm no override is copied