Pyoxidizer multiprocessing problem.

Hello, guys.
When i compile program to pyoxidizer app in windows and run it. it's give me a error:

Traceback (most recent call last):
File "multiprocessing.spawn", line 107, in spawn_main
File "multiprocessing.reduction", line 79, in duplicate
TypeError: DuplicateHandle() argument 2 must be int, not dict

#code :
```
import multiprocessing

def run_webview():
...

p = multiprocessing.Process(target=run_webview,args=())
p.start()
```

What happen?

Start by reproducing the Windows PyOxidizer build with the provided multiprocessing example and trace the failure through multiprocessing.spawn and multiprocessing.reduction. Compare the packaged application's behavior with a normal Python run; done means the cause of the DuplicateHandle TypeError is identified and multiprocessing works in the packaged app.

Written by the indexing model from the issue text.