OpenCascade on Mac -- update build system

[rckirby]

The version of opencascade on homebrew is now sufficiently modern that pythonocc can use it. Consequently, I was able to use OpenCascadeMeshHierarchy on my Mojave Mac by doing the following.

1.) Install opencascade from homebrew
2.) Clone pythonocc-core from GitHub and follow their cmake/make/make install instructions. I did this within my firedrake virtual environment. I didn't need any special options/instructions, but I did use make -j 8 to speed things up a bit (is there a way to query a reasonable number and set this in the build system?)
3.) I needed to make sure that gmsh was callable from the command line. Perhaps having the install script try to invoke gmsh and then either adding /Applications/Gmsh.app/Contents/MacOS/ to the path or creating a symlink to /Applications/Gmsh.app/Contents/MacOS/gmsh in /bin if needed should work.

If this works generally, the build system can be updated so that firedrake-install --opencascade works on Mac as well as Ubuntu.

[JDBetteridge]

@rckirby can you update on how you're currently installing opencascade et al.?

[rckirby]

Currently, brew install gives the lastest opencascade -- 7.6.3. brew info doesn't seem to show that older versions are available.

That's later than the required version for the main branch of pythonocc-core. I cloned the main branch of that repo.

cmake didn't work OOTB on that. First, one needs to brew install swig rapidjson to get some dependencies that our firedrake installer hadn't already done.

Then, I did cmake in my build directory with options:
cmake -DCMAKE_CXX_FLAGS=-I\ /opt/homebrew/include/rapidjson;/opt/homebrew/include ..

and it claimed to pass on the make/make install, but pythonocc-core/tests/run_tests.py fails with import issues:

Traceback (most recent call last):
  File "/Users/robert_kirby/Code/firedrake/src/pythonocc-core/test/run_tests.py", line 22, in <module>
    import core_wrapper_features_unittest
  File "/Users/robert_kirby/Code/firedrake/src/pythonocc-core/test/core_wrapper_features_unittest.py", line 38, in <module>
    from OCC.Core.BRepBndLib import brepbndlib_Add
ImportError: cannot import name 'brepbndlib_Add' from 'OCC.Core.BRepBndLib' (/Users/robert_kirby/Code/firedrake/lib/python3.10/site-packages/OCC/Core/BRepBndLib.py)

So either there is pythoncc-core issue or I am mis-configuring/mis-building it.

If we can clear up the pythonocc-core issue, then updating firedrake-install should be simple (adding rapidjson and swig to the brew dependencies, removing the logic to fail on Mac, and then cloning a different version of pythonocc-core.

[rckirby]

This looks like it might be a swig/name-mangling issue?