Setting up a build server:

1. Install VirtualBox, vagrant and vagrant-snap
2. In the buildserver directory, run 'vagrant up'. Will take a long time.
3. Log in with 'vagrant ssh'
4. Check it all looks ok, then 'sudo shutdown -h now'
5. Back in the main directory, run 'VBoxManage listvms' look for
   buildserver_xxxx
6. Run 'vagrant package --base buildserver_xxxx --output buildserver.box'.
   Will take a while.
7. You should now have a new 'buildserver.box'

You should now be able to use the --server option on build.py and builds will
take place in the clean, secure, isolated environment of a fresh virtual
machine for each app built.