unsymlink-lib must keep /lib64/rc/plugins in place, while moving rest of /lib64/rc to /lib/rc.
Steps to Reproduce:
1. emerge sys-boot/plymouth-openrc-plugin
2. migrate from amd64/17.0 to amd64/17.1 profile
3. emerge sys-boot/plymouth-openrc-plugin (again)
/lib64/rc/plugins/plymouth.so is moved to /lib/rc/plugins/plymouth.so. Upon re-emerge of sys-boot/plymouth-openrc-plugin, plugin is created in /lib64/rc/plugins/plymouth.so.
Plugin is used from /lib64/rc/plugins/plymouth.so. Tested this by removing /lib/rc/plugins/plymouth.so
If plugin from /lib64/rc/plugins is used, it must not be moved to /lib/rc/plugins.
Currently, move of plugins leads to untracked and unused files stored in /lib/rc/plugins.