build/ci: vote on Verified label

See internal discussion:
https://monogon.discourse.team/t/replacing-prolog-rules-by-submit-requirements/41/5

Change-Id: Id68b7153cb0ec4018ab95222cf659a79f01ef291
Reviewed-on: https://review.monogon.dev/c/monogon/+/746
Tested-by: Jenkins CI
Reviewed-by: Sergiusz Bazanski <serge@monogon.tech>
diff --git a/build/ci/jenkins-presubmit.groovy b/build/ci/jenkins-presubmit.groovy
index 37278ba..ccb75d0 100644
--- a/build/ci/jenkins-presubmit.groovy
+++ b/build/ci/jenkins-presubmit.groovy
@@ -74,6 +74,15 @@
                     }
                 }
             }
+
+            post {
+                success {
+                    gerritReview labels: [Verified: 1]
+                }
+                unsuccessful {
+                    gerritReview labels: [Verified: -1]
+                }
+            }
         }
     }
 }