Fix macOS build (#394)

There were multiple problems:

1. Firestore iOS SDK needed be upgraded to `10.3.0` in `macos/Podfile`
2. `google_sign_in_dartio ` needed to be upgraded to the latest version
3. Build Phrase script for Firebase produced an error. Therefore, I
removed this build phrase script (is only needed for crashlytics). Will
be fixed, when I try the alpha version of
invertase/flutterfire_cli#14

Closes #393

app/macos/.gitignore

@@ -4,3 +4,6 @@
 
 # Xcode-related
 **/xcuserdata/
+
+# Build artifacts
+build/

app/macos/Flutter/GeneratedPluginRegistrant.swift

@@ -23,7 +23,6 @@ import path_provider_foundation
 import pdfx
 import purchases_flutter
 import shared_preferences_foundation
-import shared_preferences_macos
 import sign_in_with_apple
 import sqflite
 import url_launcher_macos
@@ -48,7 +47,6 @@ func RegisterGeneratedPlugins(registry: FlutterPluginRegistry) {
   PdfxPlugin.register(with: registry.registrar(forPlugin: "PdfxPlugin"))
   PurchasesFlutterPlugin.register(with: registry.registrar(forPlugin: "PurchasesFlutterPlugin"))
   SharedPreferencesPlugin.register(with: registry.registrar(forPlugin: "SharedPreferencesPlugin"))
-  SharedPreferencesPlugin.register(with: registry.registrar(forPlugin: "SharedPreferencesPlugin"))
   SignInWithApplePlugin.register(with: registry.registrar(forPlugin: "SignInWithApplePlugin"))
   SqflitePlugin.register(with: registry.registrar(forPlugin: "SqflitePlugin"))
   UrlLauncherPlugin.register(with: registry.registrar(forPlugin: "UrlLauncherPlugin"))

app/macos/Podfile

@@ -27,7 +27,7 @@ require File.expand_path(File.join('packages', 'flutter_tools', 'bin', 'podhelpe
 flutter_macos_podfile_setup
 
 target 'Runner' do
-  pod 'FirebaseFirestore', :git => 'https://github.com/invertase/firestore-ios-sdk-frameworks.git', :tag => '8.9.0'
+  pod 'FirebaseFirestore', :git => 'https://github.com/invertase/firestore-ios-sdk-frameworks.git', :tag => '10.3.0'
 
   use_frameworks!
   use_modular_headers!