include could not find load file: GrSwig

I build gr-iio as described here. But it stops with

CMake Error at swig/CMakeLists.txt:36 (include):
  include could not find load file:

    GrSwig


CMake Error at swig/CMakeLists.txt:47 (GR_SWIG_MAKE):
  Unknown CMake command "GR_SWIG_MAKE".

sudo apt install swig 

was successful. What can I do better?

Thanks Andreas