Add box2d to includes

platform/unix/genmodules

@@ -106,7 +106,7 @@ inc_modules="$inc_current/modules"
 inc_libraries="$inc_current/libraries"
 
 cat > src/Makefile.am << EOF
-AM_CPPFLAGS = -I$inc_current -I$inc_modules -I$inc_libraries -I$inc_libraries/enet/libenet/include \$(LOVE_INCLUDES) \$(FILE_OFFSET)\
+AM_CPPFLAGS = -I$inc_current -I$inc_modules -I$inc_libraries -I$inc_libraries/enet/libenet/include -I$inc_libraries/box2d \$(LOVE_INCLUDES) \$(FILE_OFFSET)\
 	\$(SDL_CFLAGS) \$(lua_CFLAGS) \$(freetype2_CFLAGS)\
 	\$(openal_CFLAGS) \$(zlib_CFLAGS) \$(libmodplug_CFLAGS)\
 	\$(vorbisfile_CFLAGS) \$(theora_CFLAGS)