these 2 derivations will be built:
  /nix/store/6glplw092v3fwny9a5s7fbqyp8ilxz3p-test-drv-canary-actual.drv
  /nix/store/z2j71f545y7p8ax7hcypkx07rmpvdpfx-test-drv-canary.drv