Gitlab CI fixes

This is an attempt to fix #579 (closed) by making the tests in the cross-distro builds more tolerable so that they pass. With the tests passing we can disallow the builds to fail so that actual build issues should be caught more reliably.

Some other cleanups where necessary to make the builds pass. In particular I had to remove the i386 build because Rust is not recent enough in this image. If someone updates the image we can easily add that build back.