解决方案：
找到对应的扩展应用，并在Build Settings中搜索”Require Only App-Extension-Safe API”，其值设置为YES即可。如下图所示：
升级Xcode 12.5后辞書编译失败并报错提示”Application extensions and any libraries they link to must be built with the `APPLICATION_EXTENSION_API_ONLY` build setting set to YES.”的解决方案