Delete all Jenkins builds recursively older than a certain count

jenkins-recursive-delete.groovy

import hudson.model.*
keepCount = 10
// Some plugins - like the CB Folders - don't actually have builds.  Filter them  
jobs =  Hudson.instance.getAllItems().findAll {
  job -> job.hasProperty("lastBuild")
}

for(job in jobs)
{
  lastBuildNumber = job.lastBuild.number
  job.builds.findAll {
    build -> build.number < lastBuildNumber - keepCount
  }
  .each { 
    build -> build.delete()
  }
}