[iree.build] torch export cleanup hang with multiprocessing ‘spawn’ context

### What happened?

Related bandaid PR: https://github.com/iree-org/iree/pull/20101

Using iree.build to export torch modules (with turbine_generate build actions), we encounter an issue where weakref cleanup (?) seemingly can’t figure out what to do with the contents of the torch no.module exported, resulting in a hang during python exit.

This seemingly only happens when two conditions are satisfied:
1. We use multiprocessing ‘spawn’ context
2. The exported torch module creates tensors from class attributes or bare lists (observed with integer list) without registering them as buffers.

### Steps to reproduce your issue

coming soon…

### What component(s) does this issue relate to?

Compiler

### Version information

https://github.com/iree-org/iree/commit/028b90fd69a87b538ae8bf5e193785ffd2048f1e
(Top of main at post time)

### Additional context

_No response_