hydra: when restarting a build, remove possible failed dependencies from the failed-cache.

Dependencies

• [2] LZO3C2KI * Hack around those SQLite timeouts: just retry the transaction.
• [3] INRF7S4N Hydra: Allow all builds to be restarted.
• [4] A52HEFHQ * Allow builds to be restarted (if they failed with a transient error,
• [5] ZILILXXK * Allow scheduled builds to be cancelled. They're not removed from
• [*] LBNVQXUB * Build the /build stuff in a separate controller.
• [*] NLJJZVHO * Use ->update({...}) properly.

Change contents

• edit in src/lib/Hydra/Controller/Build.pm at line 363
  [2.42]

  [4.103]
  + my $drvpath = $build->drvpath ;
• replacement in src/lib/Hydra/Controller/Build.pm at line 365
  [4.156]→[3.0:37](∅→∅)
  − unless $build->finished;
  [4.156]

  [4.304]
  + unless $build->finished && -f $drvpath ;
• edit in src/lib/Hydra/Controller/Build.pm at line 367
  [4.305]

  [8.0]
  + my $cmd = "`nix-store -qR $drvpath`";

  + my $r = `nix-store --clear-failed-paths $cmd`;

  +