Another attempt to return ao_sndio to mpv

https://github.com/mpv-player/mpv/pull/9298

Index: wscript_build.py
--- wscript_build.py.orig
+++ wscript_build.py
@@ -248,6 +248,7 @@ def build(ctx):
         ( "audio/out/ao_pcm.c" ),
         ( "audio/out/ao_pulse.c",                "pulse" ),
         ( "audio/out/ao_sdl.c",                  "sdl2-audio" ),
+        ( "audio/out/ao_sndio.c",                "sndio" ),
         ( "audio/out/ao_wasapi.c",               "wasapi" ),
         ( "audio/out/ao_wasapi_changenotify.c",  "wasapi" ),
         ( "audio/out/ao_wasapi_utils.c",         "wasapi" ),
