Currently, the "macos-latest" runners aren't really the latest
version - on the contrary, they're running the oldest HW/OS.
Currently, there are macos-12, macos-13 and macos-14, and macos-latest
are the macos-12 ones.
The macos-14 ones run on Apple Silicon.
Previously, the macos-12 runners have usually managed to run the build
job in less than 3 hours. However, lately, the jobs often end up
taking much longer, over 5 hours, and have ended up exceeding the
6 hour timeout occasionally, even if they still also some times run
in the expected time of less than 3 hours.
Switch to the faster macos-14 runners (which can complete the build
job in around 1 h 40 min), to avoid these timeouts.