these 2 derivations will be built:
  /nix/store/jnbd9p0jrap988xniyjz0b8c697axcr7-nixos-test-driver-postgis.drv
  /nix/store/1fjzvlvr1vrb2qfzf9i4m1h4rp6idnv8-vm-test-run-postgis.drv