Force use of boost container on MacOSX

XCode 15 add memory_resource, but it needs at least macOS 14 (sonoma) at runtime which would cause the program to compile, but fail to run due to a missing symbol in the (installed) c++ runtime.

Change the logic to use boost on macOS until we upgrade the deployment target to 14 (and once we do that we'll emit a cmake warning that we should clean up the code)