This time, add:

$FLUTTER_ROOT

/packages/flutter_tools/bin/xcode_backend.sh" embed_and_thin

In other words,
the same as the main app target’s build phases.

This ensures that your Flutter app and engine are embedded
into the App Clip bundle.

Step 8 - Integrate plugins

Warning:
  CocoaPods version 1.10.0.beta.1 or higher is required
  to run Flutter apps with plugins.

8.1

Open the Podfile for your Flutter project
or add-to-app host project.

For full-Flutter apps, replace the following section:

target

'Runner'

do

use_frameworks!

use_modular_headers!

flutter_install_all_ios_pods