Update lxc-docker-git to use upstream hack/make.sh

As one of the maintainers of the upstream "hack" directory (and the included build scripts), we really request that packagers use them, and I work hard to make sure they work well for packagers. :)

I wish I had an easy way to test this for you, but my Arch-fu is not strong.  Hopefully it's close enough that you can help me adapt it the rest of the way. :)

Also, I'm willing to answer any questions or resolve any concerns you might have about this!  I'm pretty much always on IRC in the #docker channel on freenode. :+1:  They call me "packagers relations" because I'm always whining about how we can make life better for our good packagers. :cake:

(I tried to match the style of the surrounding code as best I could, and I'm sorry if I messed up anywhere, and will be happy to rebase this PR to fix it!)