Instead of using a "Pre-action" bash script to copy the Flutter framework into the BUILT_PRODUCTS_DIR, we can symlink the Flutter framework and plugins within the same directory.

Then plugins can declare a dependency on Flutter via relative path. For example, a plugin's Package.swift would look something like:

dependencies: [
  .package(name: "Flutter", path: "../Flutter"),
],

By adding an actual dependency on Flutter, Xcode now handles the copying, thinning, and codesigning of the Flutter framework. The Flutter build script should validate that Xcode is handling it correct and intervene if not.

See flutter.dev/go/swift-package-manager-plugins-v3 for more details.