GitLab

Now that apk-polkit-rs is avaiable on more arches

This reverts commit d6d720d9.

Properly set the exportDir instead

Also add gen for aarch64, since gnome-software-plugin-apk is available
on aarch64 and x86_64

Apparently they previously didn't work because the named volume
pointed to an already exisiting dir, so its contents were copied into the
docker container