This works around the lack of `sys.winver` attribute addressing the following
error:

```
 Generating C:/path/to/Python-3.12.10/Python/deepfreeze/deepfreeze.c
CUSTOMBUILD : Fatal Python error : init_import_site: Failed to import the site module [C:\path	o\pycbs-3.12-build\CMakeBuild\libpython\libpython-shared.vcxproj]
  Python runtime state: initialized
  Traceback (most recent call last):
    File "C:\path	o\pycbs-3.12-build\Lib\site.py", line 636, in <module>
      main()
    File "C:\path	o\pycbs-3.12-build\Lib\site.py", line 622, in main
      known_paths = addusersitepackages(known_paths)
                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    File "C:\path	o\pycbs-3.12-build\Lib\site.py", line 361, in addusersitepackages
      user_site = getusersitepackages()
                  ^^^^^^^^^^^^^^^^^^^^^
    File "C:\path	o\pycbs-3.12-build\Lib\site.py", line 348, in getusersitepackages
      USER_SITE = _get_path(userbase)
                  ^^^^^^^^^^^^^^^^^^^
    File "C:\path	o\pycbs-3.12-build\Lib\site.py", line 313, in _get_path
      ver_nodot = sys.winver.replace('.', '')
                  ^^^^^^^^^^
  AttributeError: module 'sys' has no attribute 'winver'
```

…ldsystem

This ensures the following tests pass:
- `test_sys` (`SysModuleTest.test_stdlib_dir`)
- `test_frozen` (`TestFrozen.test_unfrozen_submodule_in_frozen_package`)