GitHub has announced that macos-12 runners will be deprecated in December, 2024, with some temporary failures expected in November, 2024. See https://github.blog/changelog/2024-08-19-notice-of-upcoming-deprecations-and-breaking-changes-in-github-actions-runners/

A previous recently small upgrade in jdk11u GHA runners from macos-11 to macos-12 (JDK-8340671) brought the GHA checks back online on the macos platform. It is now time to upgrade from macos-12 to a later macos version.

Note that this does not require to change any current build systems, that can continue to use existing XCode versions. The scope of this enhancement is just to be able to build and run tier-1 tests on GitHub only. Future enhancements could be done in the future to ensure that other tests build properly using XCode 14. See JDK-8344458 for details.