2022.09.26 - Initial archiso ppc/ppc64le support release

This is an initial release of archiso able to generate releng images for ppc and ppc64le.

While Grub is default (currently supported through grub-mkrescue), yaboo is also supported on pmac32.

For Yaboot booting see:
https://github.com/kth5/archpower/wiki/Installation-%7C-PowerPC-Common-Problems#grub-does-not-start-or-otherwise-disables-my-installer