Non-Windows subprocess_wait: Spin x times before leaving the loop

[kazarmy]

Your checklist for this pull request

• [X] I've read the guidelines for contributing to this repository
• [X] I made sure to follow the project's coding style
• [ ] I've documented or updated the documentation of every function and struct this PR changes. If not so I've explained why.
• [ ] I've added tests that prove my fix is effective or that my feature works (if possible)
• [ ] I've updated the rizin book with the relevant information (if needed)

Detailed description

This pr is just me wondering whether spinning will fix the macos asm tests.

Test plan

The macos build is green all the time.

Closing issues

...

[kazarmy]

Closing this because the macos build failures aren't consistent enough to be able to confirm a fix.