add sndio driver

Index: drivers/SCsub
--- drivers/SCsub.orig
+++ drivers/SCsub
@@ -17,6 +17,7 @@ SConscript("alsa/SCsub")
 if env["platform"] == "ios" or env["platform"] == "macos":
     SConscript("coreaudio/SCsub")
 SConscript("pulseaudio/SCsub")
+SConscript("sndio/SCsub")
 if env["platform"] == "windows":
     SConscript("wasapi/SCsub")
     if not env.msvc:
