hooks/archiso: implement searching for archisodevice
If archisosearchuuid is specified, assign archisodevice:
- to a device with
UUID=${archisosearchuuid}, if it exists, - to a device containing
archisosearchfilename(/boot/${archisosearchuuid}.uuidby default).
This avoids having to specify archisodevice.
Related to archlinux/archiso#217 (closed)
Edited by nl6720