message: Avoid magic number.
diff: @@ -41,9 +41,10 @@ export const setSpawnParams = ctx => {
  };
  const getOutputDir = buildLog => {
  - const outputIndex = buildLog.lastIndexOf('Output directory: ');
  + const outputString = 'Output directory: ';
  + const outputIndex = buildLog.lastIndexOf(outputString);
  if (outputIndex === -1) return undefined;
  - const remainingLog = buildLog.substr(outputIndex + 18);
  + const remainingLog = buildLog.substr(outputIndex + outputString.length);
  const newlineIndex = remainingLog.indexOf('\n');
  const outputDir = newlineIndex === -1 ? remainingLog : remainingLog.substr(0, newlineIndex);
  return outputDir.trim();
  