g-octave-0.4.1-r6 installs a (generic) Makefile which uses octave_config_info in libprefix=$(DESTDIR)/`octave -H -q --no-site-file --eval "disp(fullfile(octave_config_info('libdir'),'octave'));"`; \ but recent versions of Octave (e.g. 5.1.0) don't know octave_config_info any more.