Extend macOS version check to cover other Darwin platforms

[Un1q32]

Now that the versions are all unified, we should be able to just do something like

#if defined(__ENVIRONMENT_OS_VERSION_MIN_REQUIRED__ ) && \
    __ENVIRONMENT_OS_VERSION_MIN_REQUIRED__  >= 260000

for future version checks, but for for older versions we still have to do a check for every different OS.