[devtools] Document the storage and work environment of containers used for compiling applications

Document the storage and work environment of containers used for compiling applications:
   - Where does the in-container compiler find the source codes and potential dependencies /libraries, header files, .../?
   - Where is the resulting binary stored?
   - How to handle the difference between the in-container environment and the guest system (will the executable be compiled against libraries on guest, or in the container)?
   - Persistent storage for long-term development (and repeated runs of make or other supplementary tools).