Default getfacl behavior is to remove leading slash on absolute
paths in its header printed to stdout.
Before the header it will also print a message about it...
Switches -p -or --absolute-names can turn this off
and remove some noise from our tests logs.
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.)
