If you can import the module that defines the parser, and get at the generated parser, this should be trivial to integrate with the build system. Something like:
   PYTHONPATH=. python3 -c 'import mymodule; p=mymodule.make_parser(); p.print_manpage(file="mymodule.1")'

This operation could either be done automatically during build always, or it could just be done by the developers and the man page put under version control.