Add build phase to detect nested frameworks

[mokagio]

The Hermes nested framework issue that gave us some grief could have been avoided if we had preemptively checked against that kind of setup.

The issue should be fixed now (either via #21021 or #21128) but we can benefit with this check to avoid paying the price again in the future.

How to test

See #21129 picking up the issue in the "faulty" Gutenberg version.

---

Regression Notes

1. Potential unintended areas of impact – N.A.
2. What I did to test those areas of impact (or what existing automated tests I relied on) – N.A.
3. What automated tests I added (or what prevented me from doing so) – N.A.

---

PR submission checklist:

• I have completed the Regression Notes.
• I have considered adding unit tests for my changes. N.A.
• I have considered adding accessibility improvements for my changes. N.A.
• I have considered if this change warrants user-facing release notes and have added them to RELEASE-NOTES.txt if necessary. N.A.

UI changes testing checklist: Not a UI PR.

[mokagio]

I only now notice that the shebang doesn't use Bash. Possibly why I ShellCheck warned me about having pipefail in there.

[mokagio]

We need the build phase in both WordPress and Jetpack. We cannot run this before building the apps in a centralized aggregated target because the script looks into the target's frameworks.

[wpmobilebot]

📲 You can test the changes from this Pull Request in WordPress Alpha by scanning the QR code below to install the corresponding build.

	App Name	WordPress Alpha
	Configuration	Release-Alpha
	Build Number	pr21130-723f8ed
	Version	22.7
	Bundle ID	org.wordpress.alpha
	Commit	723f8ed
	App Center Build	WPiOS - One-Offs #6425

Automatticians: You can use our internal self-serve MC tool to give yourself access to App Center if needed.

[wpmobilebot]

📲 You can test the changes from this Pull Request in Jetpack Alpha by scanning the QR code below to install the corresponding build.

	App Name	Jetpack Alpha
	Configuration	Release-Alpha
	Build Number	pr21130-723f8ed
	Version	22.7
	Bundle ID	com.jetpack.alpha
	Commit	723f8ed
	App Center Build	jetpack-installable-builds #5453

Automatticians: You can use our internal self-serve MC tool to give yourself access to App Center if needed.

[AliSoftware]

I wonder who wrote that shell script but it looks great 😃

See #21129 picking up the issue in the "faulty" Gutenberg version.

👌

I left a comment to suggest keeping the P2 post reference, as it can still be helpful for the screenshots and explanations it provides. Other than that, LGTM 👍

[mokagio]

For the record, I did not miss the RuboCop violation in CI. I decided to ignore it because it's unrelated to the changes in this PR and the Ruby code is being modified elsewhere in #21021