[Gutenberg] Apply workaround in gutenberg_post_install to address build failure

[fluiddot]

This workaround solves the issue related to redefining clockid_t in the pod RCT-Folly when using a local bundle. The issue was introduced when upgrading the React Native version to 0.71.15 in this PR, which includes further information about the workaround.

To test:

1. Check that you have the Gutenberg Mobile repository in a folder named gutenberg-mobile at the same level as the folder where WordPress-iOS repository is located.
2. Quit Xcode if needed.
3. Run rm -rf build && LOCAL_GUTENBERG=1 bundle exec pod install
4. Open Xcode.
5. Build the app and observe that no build failures are encountered.

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.
• I have considered adding accessibility improvements for my changes.
• I have considered if this change warrants user-facing release notes and have added them to RELEASE-NOTES.txt if necessary.

Testing checklist:

• WordPress.com sites and self-hosted Jetpack sites.
• Portrait and landscape orientations.
• Light and dark modes.
• Fonts: Larger, smaller and bold text.
• High contrast.
• VoiceOver.
• Languages with large words or with letters/accents not frequently used in English.
• Right-to-left languages. (Even if translation isn’t complete, formatting should still respect the right-to-left layout)
• iPhone and iPad.
• Multi-tasking: Split view and Slide over. (iPad)

[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	pr22658-29476af
	Version	24.2
	Bundle ID	com.jetpack.alpha
	Commit	29476af
	App Center Build	jetpack-installable-builds #7929

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 WordPress Alpha by scanning the QR code below to install the corresponding build.

	App Name	WordPress Alpha
	Configuration	Release-Alpha
	Build Number	pr22658-29476af
	Version	24.2
	Bundle ID	org.wordpress.alpha
	Commit	29476af
	App Center Build	WPiOS - One-Offs #8899

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

[dcalhoun]

Test plan succeeded for me. Thank you!