Merge branch 'fix-makebuildserver' into 'master'

Fix ./makebuildserver CI build

In order to get reproducible builds work reliably, we need to have buildserver create be fully automatic, and be able to run in VMs.  It should also handle caching downloads well, so that people can easily rebuild their buildserver, and CI builds don't have to download gigs and gigs for each run.  These are some related fixes.

See merge request !131