Update the include paths for the iOS Pods

One of the Pod headers includes another as FirebaseCore/FIRLoggerLevel.h, which means the directory that the pods are located in needs to be added to the include path.

PiperOrigin-RevId: 255681551

Author: a-maurice

app/CMakeLists.txt

@@ -321,6 +321,7 @@ if(IOS)
   set(base_header_dir "${pods_dir}/Pods/Headers/Public")
   target_include_directories(firebase_app
     PRIVATE
+      ${base_header_dir}
       ${base_header_dir}/FirebaseCore
       ${base_header_dir}/FirebaseDynamicLinks
       ${base_header_dir}/FirebaseInstanceID