The previous script will append an empty item of associate domains into
`Runner.entitlement` if no config has been set in the `pubspec.yaml`.

Test for automated publishing

测试自动发布脚本

test automated publishing

When no `app_id` was specified in the `pubspec.yaml`, the command will
be `ruby path_to_dir/wechat_setup.rb -a -u xxx -p xxx` which the
`app_id` will be recognized as `-u`, then inserted to the `Info.plist`.
The PR fixes the unexpected behavior.

Resolves #661

Improve Cocoapods related scripts

Adds `external-cache-path`