these 3 derivations will be built:
  /nix/store/3hpqqzmyj2fqpmyk9ikvgl0q9q7ra04q-hol_guard-3.6.1.tar.gz.drv
  /nix/store/sw21yrrqf6p8a2w7ragmsi0ikv26a98n-hol-guard-3.6.1.drv
  /nix/store/gykzs67d646fmqjn8k0rhhiq5cix6h14-check-hol-guard.drv