patch for Cuda builds

[davidkoski]

Proposed changes

• local apply of leak global CommandEncoder -- avoid cuda synchronize on process shutdown mlx#4480
• and a minimal fix for [BUG] threads and streams issues mlx#4506
• fixes crash on exit for cuda builds when using cmake

Checklist

Put an x in the boxes that apply.

• I have read the CONTRIBUTING document
• I have run pre-commit run --all-files to format my code / installed pre-commit prior to committing changes
• I have added tests that prove my fix is effective or that my feature works
• I have updated the necessary documentation (if needed)

[nwh]

LGTM