def yarn_preinstall_binary_path
    return @yarn_preinstall_binary_path if defined?(@yarn_preinstall_binary_path)

    path = run("which yarn").strip
    if path && $?.success?
      @yarn_preinstall_binary_path = path
    else
      @yarn_preinstall_binary_path = false
    end
  end
Example `tmp/build_8523f77fb96a956101d00988dfeed9d4/.heroku/yarn/bin/yarn`