code: async function prepareForPreprocess (isolateLogPath) {
    const dest = isolateLogPath + '.preprocess-ready'
    let data = await readFile(isolateLogPath, { encoding: 'utf8' })
    data = data.split('\n').filter((s) => s.length < 1024).map(fixLines).join('\n')
    await writeFile(dest, data)
    return dest
  }
docs: 1. Filter because long lines make the --preprocess crash. Filter them beforehand, because Node.js 8.12.0 would crash if there is any error in the preprocess script 2. Escape backslashes because V8's --preprocess -j treats \\ as an escape pattern, garbling Windows paths or regular expression definitions that contain it TODO use streams