Use pkg-config to determine flags

[BenjaminRodenberg]

Closes #5.

@fsimonis: One thing I'm worrying a bit: What if a user does not have pkg-config installed? Or would you just take this as granted?

[BenjaminRodenberg]

It looks like the "user" precice/precice is already causing trouble here. Locally everything worked nicely.

[fsimonis]

One thing I'm worrying a bit: What if a user does not have pkg-config installed? Or would you just take this as granted?

I would not take this for granted, but it is available everywhere (even on Windows).
There should be no issue requiring this.

Also, keep in mind that the majority of our adapters rely on pkg-config.

[fsimonis]

@BenjaminRodenberg FYI, the pkg-config package is not installed in the current precice/precice:latest (25.10 16:15).

[ajaust]

I vote for obtaining the include and link flags for preCICE. Otherwise, it seems to be pretty hard/impossible to build the bindings on MacOS. According to some blog posts LD_LIBRARY_PATH and DYLD_LIBRARY_PATH are not forwarded to subprocesses anymore due to the security measure in MacOS X. Obtaining the necessary flags seems to help. This is also connected to #139.

However, this still leaves us with the problem of using the Python bindings on MacOS X. We could try set the rpath for the bindings, but then the bindings get (less) portable. I am not sure if that would be a problem.

Is there any opinion on how well or whether to support MacOS x?

[ajaust]

And another note... If we want to use pkg-config we could also think about using the pkgconfig package available in Python which would maybe make the setup files look a bit nicer.

[IshaanDesai]

The python package pkgconfig is now used to determine preCICE flags in the bindings. This was implemented in #149