these 4 derivations will be built:
  /nix/store/0yjb7gwprfb9b14vivbslln9ahxa3sxi-source.drv
  /nix/store/gnq1q9w4c6kjy2kjm40rk00flz8yg7qm-omp-18.0.6-cargo-vendor-vendor-staging.drv
  /nix/store/mhmw492d7yc061xsqypcd0h4sj405m5i-omp-18.0.6-cargo-vendor-vendor.drv
  /nix/store/nd9wcy9b7fl9ivxwgv895k08j39idfb3-omp-18.0.6.drv