Delete Old Builds Jenkins Script

script.groovy

//you can go to Manage Jenkins > Script Console
import jenkins.model.Jenkins
import hudson.model.Job

MAX_BUILDS = 55
Jenkins.instance.getAllItems(Job.class).each { job ->
  println job.name
  def recent = job.builds.limit(MAX_BUILDS)
  for (build in job.builds) {
    if (!recent.contains(build)) {
      println "Preparing to delete: " + build
      build.delete()
    }
  }
}