arch-chroot: add option to preserve the chroot resolv.conf
Created by: evelikov
There is a comprehensive inline comment about why we're touching the chroot resolv.conf. Although it does not consider the cases where:
- the link may be broken for specific reasons, and/or
- working resolver within the chroot is not wanted
Note: there is a set of minor conflicts with a few other MR https://github.com/archlinux/arch-install-scripts/pull/48 and https://github.com/archlinux/arch-install-scripts/pull/49, so I've decided to include them here as a base. Happy to reshuffle the lot.