Repairing warnings and error regarding Version.h by using pkgconfig to link to preCICE

[IshaanDesai]

This PR resolves a warning and an error in the action set of build-and-test. The warning was:

warning: cyprecice/cyprecice.pyx:1211:57: local variable '_value' referenced before assignment

and the error was

/home/runner/work/python-bindings/python-bindings/precice/SolverInterface.hpp:7:10: fatal error: precice/Version.h: No such file or directory
    7 | #include "precice/Version.h"
      |          ^~~~~~~~~~~~~~~~~~~

[IshaanDesai]

In finding a solution to include the generated header Version.h in the mock testing workflow, the Python package pkgconfig is used to link the bindings to preCICE. This implementation was already discussed and partially done in #135, and a full solution in consultation with @fsimonis is done here.

[BenjaminRodenberg]

Overall I think using pkgconfig makes a lot of sense here.

The issue with precice/precice vs. precice/precice:2.4.0 might be an upstream issue, but maybe this is also an argument to change things upstream?

One thing that might be affected by this change: Do you need updates for the spack recipe?

[fsimonis]

One thing that might be affected by this change: Do you need updates for the spack recipe?

Yes.
Currently, spack is failing due to py-pkgconfig missing during build. I assume this based on the build failing during processing of the pyproject.toml file.

[BenjaminRodenberg]

I still have some minor points w.r.t to the mocking of preCICE. Can you try to remove the build process of preCICE and the installation of the dependencies, if it is not absolutely needed? I think it should work without building preCICE.

[BenjaminRodenberg]

After some clarifications I cannot find anything to complain anymore. Thanks for the explanations @IshaanDesai 🙏