On an otherwise wasted day with no concrete output
Given a PKGBUILD,
makepkg to package it,
repo-add to add it to a database.db.tar,
save in the same flat directory
There is an official image at archlinux/base
If you insist on diy: review pacstrap
basically mkdirs,
then pacman -r $root -Syu pacman
(pacman depends on everything you will ever need...)
kaniko/executor has different behaviour from docker build
it mounts docker.sock into the container and uses more symlinks
COPY --from=build /build / in s scratch container works in docker but not kaniko