add sndio

backport commit 0b3496f:
Add support for SDL3 joystick input driver

Index: drivers/SCsub
--- drivers/SCsub.orig
+++ drivers/SCsub
@@ -12,6 +12,7 @@ SConscript("windows/SCsub")
 SConscript("alsa/SCsub")
 SConscript("coreaudio/SCsub")
 SConscript("pulseaudio/SCsub")
+SConscript("sndio/SCsub")
 if env["platform"] == "windows":
     SConscript("wasapi/SCsub")
 if env["xaudio2"]:
@@ -30,6 +31,11 @@ if env["platform"] != "server":
     SConscript("gl_context/SCsub")
 else:
     SConscript("dummy/SCsub")
+
+# Input drivers
+if env["sdl"] and env["platform"] in ["x11", "macos", "windows"]:
+    # TODO: Evaluate support for Android, iOS, and Web.
+    SConscript("sdl/SCsub")
 
 # Core dependencies
 SConscript("png/SCsub")
