[powerpc64le][riscv64] Use ArchPOWER as base distro
ArchPOWER is an unofficial powerpc64le, powerpc and riscv64 port of Arch Linux. I have not tested it, but I think it is worth to take a look at and consider it as a candidate to import packages from. This would save us a lot of time and effort, just like we do with Arch32 and ALARM.
It works with only two repos, [base] and [testing], and by taking a fast look at them, packages seem pretty up to date and has most (all?) official Arch packages. However, as I've not tested it, idk if some of them may be broken, like many of Arch32.