add fakechroot dependency in README.md, prevent 'already exists' error when running ln -s by adding -f in Makefile, combine two layers of Dockerfile and fix typo of pugring.gpg~

Signed-off-by: Linux Ninja <linuxninja@bryangay.com>

When building the image for publishing in the infrastructure, we need a
rootfs that's <100MB, due to github filesize restrictions (this, plus
the fact that there's no git-lfs support for building in the docker
library toolchain). Compress the rootfs image so that it can be
hosted on github.

LICENSE: add license 

Add secondary mirror that itself redirects to various locations:
https://www.archlinux.org/mirrors/rackspace.com/

The old Dockerfile and Makefile pair didn't meet the requirements of the
ci-test. Namely, the (very sensible )requirement of not shipping a
private key was missing, the sysusers hook wasn't executed properly and
the /var/cache/pacman/pkg folder was remoed (and it's specified in the
pacman MTREE package)

I commited the wrong Dockerfile.

The previous makefile assumed that PWD was populated. This doesn't
happen in certain cases (e.g., when running as a systemd unit). Make
sure we have the PWD variable set before running any target.

This commit adds:

- Systemd sysusers hook is ran on the dockerfile
- The dockerfile also populates the archlinux keyring
- Remove the libalpm hooks as they are uneccessary now
- Moved the package cleanup before the tar step on the makefile

The old makefile required commands to be run as a superuser, which
may become problematic when deploying on the archlinux infrastructure.
Use fakeroot and regular pacman commands to allow for to bootstrap a
rootfs.

Use the most minimal package set