Add sdl mixer

You can now play audio and sound effects! I can guarantee that this doesn't work on Windows or Mac, but this is a start. I only got it working on my Linux.

Need to get the lib-files (.dll and .a) for Windows and do some more testing so this actually works on all platforms.

dependencies/subprojects/sdl2_mixer_windows/lib/libSDL2_mixer.la

@@ -17,7 +17,7 @@ old_library='libSDL2_mixer.a'
 inherited_linker_flags=''
 
 # Libraries that this one depends upon.
-dependency_libs=' -L/tmp/tardir/SDL2_mixer-2.8.1/VisualC/external/optional/x64 -L/home/runner/work/SDL_mixer/SDL_mixer/deps/mingw-deps/x86_64-w64-mingw32/lib -lmingw32 /home/runner/work/SDL_mixer/SDL_mixer/deps/mingw-deps/x86_64-w64-mingw32/lib/libSDL2.la -ldinput8 -ldxguid -ldxerr8 -luser32 -lgdi32 -limm32 -lole32 -loleaut32 -lshell32 -lsetupapi -lversion -luuid -lwinmm'
+dependency_libs=' -L/tmp/tardir/SDL2_mixer-2.8.1/VisualC/external/optional/x64 -L/opt/local/x86_64-w64-mingw32/lib -lmingw32 /opt/local/x86_64-w64-mingw32/lib/libSDL2.la -ldinput8 -ldxguid -ldxerr8 -luser32 -lgdi32 -limm32 -lole32 -loleaut32 -lshell32 -lsetupapi -lversion -luuid -lwinmm'
 
 # Names of additional weak libraries provided by this library
 weak_library_names=''