Building environments (`make install-all-python`) fails on Intel Macs

[pcustic]

Initial Checks

• I confirm that I'm using the latest version of Pydantic AI
• I confirm that I searched for my issue in https://github.com/pydantic/pydantic-ai/issues before opening this issue

Description

While working on another pull request, after pulling in latest changes from upstream, I noticed I cannot build environments for Pydantic AI on my Intel MacBook anymore.

It turns out the culprit is recently merged PR that introduced some libraries (at least mlx) that don't have builds for Intel Macs.

Example Code

On Intel MacBook and with the latest code from main run:

make install-all-python

or 

make test-all-python

Python, Pydantic AI & LLM client version

All versions of Python.