Summary:
* Update tutorial due to recent changes.
* Clean up setup.sh for app helper lib build.

Pull Request resolved: https://github.com/pytorch/executorch/pull/2962

Reviewed By: cccclai

Differential Revision: D55951189

Pulled By: kirklandsign

fbshipit-source-id: 2c95e8580145b039f503e7cd99a4003867f8dbb0
(cherry picked from commit 26365f188fa7526e4b6a9d67ff4a976f81487598)