Always install the ephemeral engine copy instead of fetching from CocoaPods specs (#37906)

dev/devicelab/bin/tasks/module_test_ios.dart

@@ -187,6 +187,15 @@ Future<void> main() async {
         return TaskResult.failure('Failed to build ephemeral host .app with CocoaPods');
       }
 
+      final File podfileLockFile = File(path.join(projectDir.path, '.ios', 'Podfile.lock'));
+      final String podfileLockOutput = podfileLockFile.readAsStringSync();
+      if (!podfileLockOutput.contains(':path: Flutter/engine')
+        || !podfileLockOutput.contains(':path: Flutter/FlutterPluginRegistrant')
+        || !podfileLockOutput.contains(':path: Flutter/.symlinks/device_info/ios')
+        || !podfileLockOutput.contains(':path: Flutter/.symlinks/package_info/ios')) {
+        return TaskResult.failure('Building ephemeral host app Podfile.lock does not contain expected pods');
+      }
+
       section('Clean build');
 
       await inDirectory(projectDir, () async {

packages/flutter_tools/templates/module/ios/host_app_ephemeral_cocoapods/Podfile.copy.tmpl

@@ -4,6 +4,7 @@ flutter_application_path = '../'
 load File.join(flutter_application_path, '.ios', 'Flutter', 'podhelper.rb')
 
 target 'Runner' do
+  install_flutter_engine_pod
   install_flutter_plugin_pods flutter_application_path
 end