Using pkgs.lib on the spine of module evaluation is problematic
because the pkgs argument depends on the result of module
evaluation. To prevent an infinite recursion, pkgs and some of the
modules are evaluated twice, which is inefficient. Using ‘with lib’
prevents this problem.
Needed for the installer tests, since otherwise mounting a filesystem
may fail as it has a last-mounted date in the future.
http://hydra.nixos.org/build/9846712
Now that overriding fileSystems in qemu-vm.nix works again, it's
important that the VM tests that add additional file systems use the
same override priority. Instead of using the same magic constant
everywhere, they can now use mkVMOverride.
http://hydra.nixos.org/build/6695561
It requires a writable /nix/store to store the build result. Also,
wait until we've reached multi-user.target before doing the build, and
do a sync at the end to ensure all data to $out is properly written.
http://hydra.nixos.org/build/6496716
