PR for archbuilder

[Rob Cohen]

I just submitted a PR for qubes-builder-archlinux:

https://github.com/QubesOS/qubes-builder-archlinux/pull/25

before the tarball filename was incorrectly generated and cause the PR to fail.

I also cleaned up the code a bit and made it more compliant with Bash best practices.

It seems to be working on a clean debian qube, if someone could test I would appreciate it.

Thanks,

Rob Cohen
https://rcohen.me