Allow pod version overrides (#2589)

packages/admob/RNFBAdMob.podspec

@@ -0,0 +1,32 @@
+require 'json'
+package = JSON.parse(File.read(File.join(__dir__, 'package.json')))
+
+firebase_sdk_version = '~> 6.5.0'
+using_custom_firebase_sdk_version = defined? $FirebaseSDKVersion
+if using_custom_firebase_sdk_version
+  Pod::UI.puts "RNFBAdMob: Using user specified Firebase SDK version '#{$FirebaseSDKVersion}'"
+  firebase_sdk_version = $FirebaseSDKVersion
+end
+
+Pod::Spec.new do |s|
+  s.name                = "RNFBAdmob"
+  s.version             = package["version"]
+  s.description         = package["description"]
+  s.summary             = <<-DESC
+                            A well tested feature rich Firebase implementation for React Native, supporting iOS & Android.
+                          DESC
+  s.homepage            = "http://invertase.io/oss/react-native-firebase"
+  s.license             = package['license']
+  s.authors             = "Invertase Limited"
+  s.source              = { :git => "https://github.com/invertase/react-native-firebase.git", :tag => "v#{s.version}" }
+  s.social_media_url    = 'http://twitter.com/invertaseio'
+  s.ios.deployment_target = "9.0"
+  s.source_files        = 'ios/**/*.{h,m}'
+  s.dependency          'React'
+  s.dependency          'Firebase/Core', firebase_sdk_version
+  s.dependency          'Firebase/Analytics', firebase_sdk_version
+  s.dependency          'Firebase/AdMob', firebase_sdk_version
+  s.dependency          'PersonalizedAdConsent'
+  s.dependency          'RNFBApp'
+  s.static_framework    = true
+end