Don't set empty string when remove ccache (#45400)

Summary:
After `pod install`, it would set some empty flags, which seems useless. cc cipolleschi .

![image](https://github.com/user-attachments/assets/fb795c61-0838-4522-a34b-cde469467b3b)

## Changelog:

[IOS] [FIXED] - Don't set empty string when remove ccache

Pull Request resolved: https://github.com/facebook/react-native/pull/45400

Test Plan: No empty flags should be set after we exec `pod install`.

Reviewed By: cortinico

Differential Revision: D59671357

Pulled By: cipolleschi

fbshipit-source-id: 26b55da9efaeed36876649cc27f09ecafaba412a