[flutter_tools] pod install waiting too long at 'Generating Pods project' in add2app host project

### Steps to reproduce

1. An existing host iOS Project that contains about 300 cocoa pods dependencies
2. Add a Flutter module to this project according to doc https://docs.flutter.dev/add-to-app/ios/project-setup
3. Run `pod install` under host iOS project

### Expected results

`pod install` finish not too late than before

### Actual results

`pod install` hangs on 'Generating Pods project'

### Code sample

Code sample

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### Screenshots or Video

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### Logs

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### Flutter Doctor output

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