This prevents a dependency on liblapack (which randomly fails) and
TeXlive (which is huge).
http://hydra.nixos.org/build/14897240
(cherry picked from commit b9bde98161d09496421efbaafe5219cc84d05f5b)
You can now run a test in the nixos/tests directory directly using
nix-build, e.g.
$ nix-build '<nixos/tests/login.nix>' -A test
This gets rid of having to add the test to nixos/tests/default.nix.
(Of course, you still need to add it to nixos/release.nix if you want
Hydra to run the test.)
