Merge branch 'caching-for-makebuildserver' into 'master'

two quick kinds of caching for makebuildserver

I've been running `./makebuildserver` on a machine that only connects to the internet via Tor.  That means slow internet and other issues.  These two small changes made it easier to run `./makebuildserver` in this setup.  In combination with !25, this would give good support for working in low bandwidth environments.

See merge request !67