Delete artifacts when restarting build

Summary: Fixes T4336.  This updates the build engine to delete all artifacts when targets are being deleted.  This prevents conflicts when builds are restarted.

Test Plan: Restarted a build that had a lease host step and it didn't crash.

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley

CC: Korvin, epriestley, aran

Maniphest Tasks: T4336

Differential Revision: https://secure.phabricator.com/D8092

src/applications/harbormaster/engine/HarbormasterBuildEngine.php

@@ -101,6 +101,22 @@ final class HarbormasterBuildEngine extends Phobject {
       ->setViewer($this->getViewer())
       ->withBuildPHIDs(array($build->getPHID()))
       ->execute();
+
+    if (!$targets) {
+      return;
+    }
+
+    $target_phids = mpull($targets, 'getPHID');
+
+    $artifacts = id(new HarbormasterBuildArtifactQuery())
+      ->setViewer($this->getViewer())
+      ->withBuildTargetPHIDs($target_phids)
+      ->execute();
+
+    foreach ($artifacts as $artifact) {
+      $artifact->delete();
+    }
+
     foreach ($targets as $target) {
       $target->delete();
     }