Fix Firestore builds on non-Apple platforms
Fix Firestore builds on non-Apple platforms

settings_ios is only used for Apple platforms, so filter it out.

PiperOrigin-RevId: 299209107

firebase/firebase-cpp-sdk,firebase/firebase-cpp-sdk,firebase/firebase-cpp-sdk,firebase/firebase-cpp-sdk,firebase/firebase-cpp-sdk,firebase/firebase-cpp-sdk,firebase/firebase-cpp-sdk,firebase/firebase-cpp-sdk