code: function buildToFile(compileOptions, startTime) {
    utils.header()
    utils.log()
    utils.log(emoji.go, 'Building...', chalk.bold.cyan(compileOptions.inputFile))
  
    return compile(compileOptions).then(result => {
      utils.writeFile(compileOptions.outputFile, result.css)
  
      const prettyTime = prettyHrtime(process.hrtime(startTime))
  
      utils.log()
      utils.log(emoji.yes, 'Finished in', chalk.bold.magenta(prettyTime))
      utils.log(emoji.pack, 'Size:', chalk.bold.magenta(bytes(result.css.length)))
      utils.log(emoji.disk, 'Saved to', chalk.bold.cyan(compileOptions.outputFile))
      utils.footer()
    })
  }
docs: Compiles CSS file and writes it to a file.
  
  @param {CompileOptions} compileOptions
  @param {int[]} startTime
  @return {Promise}