pybind11_add_module does not take include directories as input.

[SergioRAgostinho]

Pybind's addmodule does not take include directories as inputs. It consumes source .cpp files.

On my system this was generating the following error

-- Configuring done
CMake Error at pybind11/tools/pybind11Tools.cmake:131 (add_library):
  Cannot find source file:

    /<redacted>/Development/include/eigen3

  Tried extensions .c .C .c++ .cc .cpp .cxx .m .M .mm .h .hh .h++ .hm .hpp
  .hxx .in .txx
Call Stack (most recent call first):
  CMakeLists.txt:32 (pybind11_add_module)