For whatever reason CMake seems to infer "12.6" as SDK version, because the GitHub Action macOS runner is based on macOS 12.6. But that number doesn't match the SDK version, which should be 13.1 here.
Though I can't tell if it's a CMake bug or a GitHub Actions image setup issue.
It's a bit sad to have to hardcode the value, and it means it might break again next time GitHub Actions update their macos-12 image, if they remove the 13.1 SDK. If anyone feels like digging into it further, feel free to. :)
For whatever reason CMake seems to infer "12.6" as SDK version, because the GitHub Action macOS runner is based on macOS 12.6. But that number doesn't match the SDK version, which should be 13.1 here.
This seems to be a long running issue with GitHub Actions' macOS runner: https://github.com/actions/runner-images/issues/2211
Though I can't tell if it's a CMake bug or a GitHub Actions image setup issue.
It's a bit sad to have to hardcode the value, and it means it might break again next time GitHub Actions update their
macos-12image, if they remove the13.1SDK. If anyone feels like digging into it further, feel free to. :)