Python interface build process cannot find necessary headers

Certain python distributions (namely the one provided by Homebrew on macOS) do not provide the system include paths when building the python bindings, resulting in build failure.

See https://github.com/thliebig/openEMS-Project/discussions/167#discussioncomment-7903125 for more details.

Possible fixes

Figure out a cross-platform way of finding the default system include paths and specify them explicitly
Modify the compiler flags (in a way supported by both clang and gcc) so that system include paths will not be overwritten
Modify the directory structure (or use a symlink) so that header files are present in the same directory as the python input files
Modify references to headers to use headers in the repository via a relative path

Also https://github.com/thliebig/openEMS/issues/135

thliebig / CSXCAD

Python interface build process cannot find necessary headers #38