These stages are in particular:
* Install of the bare Windows VM with Cygwin and shut down.
* Boot up the same VM again without the installation media and dump the
VMs memory to state.gz.
* Resume from state.gz and build whatever we want to build.
Every single stage involves a new "controller", which is more like an
abstraction on the Nix side that constructs the madness described in
276b72fb93.
Signed-off-by: aszlig <aszlig@redmoonstudios.org>
