these 3 derivations will be built:
  /nix/store/17j7sdc935mri6l2gpplxii32zl83v1p-source.drv
  /nix/store/agnx2f11jlj4pxpm97lp5vfl4q4kizpn-harmonia-deps-3.2.0.drv
  /nix/store/gz91qr9xn8z74y6j69rg0kil4c94xsxm-harmonia-llvm-cov-3.2.0.drv