code: func removeStaledBuilds(testData TestToBuildData, job, test, node, build string) {
  	key := job + "_" + test + "_" + node
  	count := len(buildFIFOs[key])
  	if count == 0 || buildFIFOs[key][count-1] != build {
  		// A new build comes.
  		buildFIFOs[key] = append(buildFIFOs[key], build)
  		count++
  	}
  	if count > *builds {
  		delete(testData[test].Data[node], buildFIFOs[key][0])
  		buildFIFOs[key] = buildFIFOs[key][1:]
  	}
  }
docs: // removeStaledBuilds ensures that the testData only contains data for --builds
  // number of builds by removing staled build data.