Guidance on external .lib usage in c++ OOT appreciated

The GR Tutorials are really helpfull to learn, but as a beginner I got stuck in creating a C++ OOT block interacting with an external gpio lib.
My objective (for now to learn to use the lib in an OOT) is to control an external LED when a flowgraph starts. When this works, I'll use gpio input pins in the working part of an OOT source block.

I dont ask you to solve the problem for me, but.. any guidance where look finding the root cause is highly appreaciated. Summarized:
- Separate from gnr the led_on code (driving a gpio-output pin) runs succesfull.
- the existing gnr C++ OOT tutorial is the starting point to implement the LED control.
- The added start() function in the attached OOT block prints succesfully a "Hello GNU Radio World" test message in the GRC terminal window.
- When the hardware LED/GPIO-code (lines 55-75) are uncommented, the compiling proces of multDivSelect_impl.cc goes well, but...
- When the flowgraph is started results in an error "from gnuradio import customModule referring to /customModule/__init__.py

Your guidance/direction to this beginner is highly appreciated.

Robert

ps. to avoid mailing list server load:Thanks for having a look at code & logs here:
https://tinyurl.com/GNRreachout20250407