1549 macOS import fails due to incorrect runtime library lookup (RPATH)

[HenrZu]

Changes and Information

Please briefly list the changes (main added features, changed items, or corrected bugs) made:

• Fix build error due to long/unsigned long
• Fix macOS runtime/import error due to an incorrect RPATH in the Python bindings

If need be, add additional information and what the reviewer should look out for in particular:

• Im not adding a dedicated macOS CI job as part of this change. We currently don’t have macOS hardware available for validation. This PR fixes the reported macOS-specific build/import issues, but broader macOS CI coverage should be handled separately.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.40%. Comparing base (99275bc) to head (6e3df55).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1550      +/-   ##
==========================================
- Coverage   97.41%   97.40%   -0.02%     
==========================================
  Files         190      190              
  Lines       16858    16866       +8     
==========================================
+ Hits        16422    16428       +6     
- Misses        436      438       +2     

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[reneSchm]

Changes to the big int PickleType's are good, it probably should have been like that from the start.

I am not sure I fully understand the whole rpath situation, the cmake docs mention different variables for windows and apple, but no defaults for CMAKE_INSTALL_RPATH. It is also implied that only Linux uses rpaths at all?