Have Actions Workflows use macos-13 rather than macos-12

[philrz]

What's Changing

Our GitHub Actions Workflows that previously used the Intel-based macos-12 runners will now use the Intel-based macos-13 runners.

Why

GitHub notified:

GitHub Actions: The macOS 12 runner image will be removed by 12/3/2024

Details

The full text of the notification email:

I've tended toward always using the oldest available runners for each target platform since we expect at least some users are running older OS versions (conservative corporate environments, etc.) and this gives us a better chance of knowing if something unexpected has caused us to lose the ability to run on the older OSes such that we'd need to update our Supported Platforms statement. Since GitHub has given us this early notice, I figure we might as well make the jump to the newer OS ASAP.

Another consideration is that we surely still have some users out there stuck on older Intel-based Macs (I'm one of them 😛) so we'd like to continue offering builds for these as long as possible. Thankfully the Actions Runners for macos-13 are still Intel based:

Mac-1729112151240:~ runner$ uname -a
Darwin Mac-1729112151240.local 22.6.0 Darwin Kernel Version 22.6.0: Wed Jul 31 21:42:48 PDT 2024; root:xnu-8796.141.3.707.4~1/RELEASE_X86_64 x86_64

Mac-1729112151240:~ runner$ sw_vers
ProductName:		macOS
ProductVersion:		13.7
BuildVersion:		22H123

While macos-14 and newer are M1.

Mac-1729112489822:~ runner$ uname -a
Darwin Mac-1729112489822.local 23.6.0 Darwin Kernel Version 23.6.0: Wed Jul 31 20:50:13 PDT 2024; root:xnu-10063.141.1.700.5~1/RELEASE_ARM64_VMAPPLE arm64

Mac-1729112489822:~ runner$ sw_vers
ProductName:		macOS
ProductVersion:		14.7
BuildVersion:		23H124

So having the ability to jump to macos-13 buys us some time before we need to make a decision on if we figure out some cross-compiled approach to making Intel builds or just start supporting only M1.

Finally, taking care of this made me realize that when I added the ability to build on M1 several months ago, I forgot to update the Supported Platforms statement, so I've done that here.