these 2 derivations will be built:
  /nix/store/9mjmy3xrfc9f9g8jm361c00am317yg96-test-drv-canary-actual.drv
  /nix/store/f1jd51cmh4wcq1wvxg4wznvxkyi7q7s5-test-drv-canary.drv