Fix a missing variable.

Change-Id: I6ff2a63ed9c10b149d21c64943ceeeccf30d4d82
diff --git a/cicd/pipelines/tasks/task_update_mirrors.jenkins b/cicd/pipelines/tasks/task_update_mirrors.jenkins
index 2299a05..f2725a3 100644
--- a/cicd/pipelines/tasks/task_update_mirrors.jenkins
+++ b/cicd/pipelines/tasks/task_update_mirrors.jenkins
@@ -3,7 +3,7 @@
 library 'functions'
 
 def workspacePath = "/home/jenkins/workspace"
-def buildLabel = "${targetName}-${UUID.randomUUID().toString()}"
+def buildLabel = "task.update.mirrors-${UUID.randomUUID().toString()}"
 def sourcePath = "${workspacePath}/src"
 
 // FIXME(jtgans): Get rid of privileged! This is a security risk!