Fix for 5561: Apple maintains two stable versions of Xcode, update BUILDING.md to reflect that

[MrRage]

Calling out the latest OS helps disambiguate which stable version we are talking about.

First-time contributor checklist

• [X] I have read the README and CONTRIBUTING documents
• [X] I have signed the Contributor Licence Agreement

Contributor checklist

• [X] My commits are rebased on the latest main branch

• [X] My commits are in nice logical chunks

• [X] My contribution is fully baked and is ready to be merged as is

• [X] I have tested my contribution on these devices:

  • Macbook Pro: TextMate and Xcode

• ---

Description

Apple maintains two stale versions of Xcode when transitioning from one OS to another, so I thought we could specify that we were talking about the latest OS. Stable versions of Xcode 13 will not build Signal but Xcode 14 will.

[stale[bot]]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[stale[bot]]

This issue has been closed due to inactivity.