While we will only outwardly support Windows 10+, due to an issue in
mingw-w64, we can't set the *-subsystem-version values higher than to
target Windows 8, so do that as a best effort.
Running Bitcoin Core on unsupported OSes may expose users to security
issues.
macOS Monterey 12 received its final security update (12.7.6) on July
2024. Apple classifies the hardware that can run macOS 12 at most as
"obsolete worldwide".
