please apply my makefile path here.
renamed LDFLAGS to LIBS, changed link order
it is necessary for LDFLAGS like -Wl,--as-needed.
you can read more about that here: http://www.gentoo.org/proj/en/qa/asneeded.xml
you can leave the -lSDL_mixer there but it would be fine if you add a target nosound so that we can use make nosound or similar.
(maybe a point of interest https://bugs.gentoo.org/show_bug.cgi?id=247101 )