Fix msys by adding BINDIR to search path

[ktbarrett]

Closes #60.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 7 lines in your changes missing coverage. Please review.

Project coverage is 62.78%. Comparing base (95b8993) to head (8783cd8).

Files with missing lines	Patch %	Lines
src/find_libpython/__init__.py	0.00%	6 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #62      +/-   ##
==========================================
- Coverage   62.89%   62.78%   -0.12%     
==========================================
  Files           4        4              
  Lines         221      223       +2     
  Branches       47       48       +1     
==========================================
+ Hits          139      140       +1     
  Misses         61       61              
- Partials       21       22       +1     

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[ktbarrett]

I'll fix alpine separately. I'm not sure what's going on, py3-nox should be version 2024.10.09 and doesn't use attrs.