GoogleSignIn required to be signed in Xcode

This seems like a new development, but GoogleSignIn is being required to be signed. This is quite strange for a CocoaPod. This means I need to alter the Pods project and add the signing information to only the GoogleSignIn project. What is the deal with this? It's creating distribution headaches too.

首先检查原始报告和链接的已关闭 pull request #226；该 issue 未指定文件、测试或入口点。确定 CocoaPods GoogleSignIn 项目是否仍在 Xcode 中被不必要地签名，以及预期的分发行为是什么。只有就签名要求和分发设置达成一致的解决方案后，才算完成。

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