Distribute opencascade includes as part of cabal sources to fix Nix Integration and improve build reproducibility on different systems

[KovalevDima]

Currently opencascade-hs binds to system state by linking to absolute system path /usr/include/opencascade. We can't dynamically link to headers files paths, since opencascade doesn't distribute pkg-config file. So we can only copy all of the header files locally to make project build reproducible on different systems.

In this PR I've copied all of the /include/opencascade files (of version 7.8.1) and configured cabal to use them. After that I was able to build opencascade-hs on my Haskell+Nix project (which translates cabal project to Nix via cabal2nix). Windows build won't work with current bind path too. I think this PR should make this library buildable on windows too, but I'm not able to test it

Not sure if it's best way to fix this problems, but it works

[KovalevDima]

I have not patched package.yaml since I'm not using stack and can test if it's work

[joe-warren]

Hi Kovalev, thanks for your work on this

As a heads up, I'm currently pretty reluctant to merge anything that relies on vendoring the underlying C++ library

[joe-warren]

Thanks for your work, but I'm going to close this, I think #12 makes it redundant?

Do feel free to re-open if you disagree?

[KovalevDima]

Hi
The difference between this change and #12 is that current PR fixes underlying C++ library version and distributes it as a part of Haskell library sources. So the current change will fix build for nixpkgs via hackage2nix (and probably improve UX on Windows) while change from #12 requires to manually setup project with Nix flakes overlay and will work only in context of such flake. In my opinion it would be better to have pkg-config for C++ sources which requires to work with maintainers of underlying library

I'm not a library user so it's not important for me to deliver current solution into upstream. This PR was more like a demonstration of possible solution to improve build reproducibility which involves some trade-offs that you may not agree with. So feel free to close this PR and repeat the same steps that I did yourself if you will find this change satisfying in future