Fix restarting a build

Dependencies

• [2] J5ITV54P Make restartBuilds faster
• [3] VHV6GI4L Add a jobset eval action to restart all aborted/cancelled builds
• [*] 2GK5DOU7 * Downloading closures.

Change contents

• replacement in src/lib/Hydra/Helper/Nix.pm at line 452
  [3.994]→[3.994:1036](∅→∅)
  − push @paths, $build->drvpath;
  [3.994]

  [2.21]
  + push @paths, $_->path foreach $build->buildoutputs->all;