Port to a cross-platform buildsystem
GNU Makefiles did the trick for Jump 'n Bump so far as it's a relatively simple project, but to provide better cross-platform support it would be worth considering alternative buildsystems. CMake comes to mind, it's relatively popular nowadays and I'm much more confident with it than with autotools, but I'm open to alternatives.
Moving away from Makefiles should help fix #21 (closed) (it might be fixable while sticking to Makefiles though, but so far my attempts have been in vain).