these 2 derivations will be built:
  /nix/store/p0f0h0fkqniii51qyzkkqk49wlrwhgjm-test-drv-canary-actual.drv
  /nix/store/l50pc4bmx1njmgp5pbm7r3zc94dzbcgc-test-drv-canary.drv