patch 9.0.0694: no native sound support on Mac OS

Problem:    No native sound support on Mac OS.
Solution:   Add sound support for Mac OS. (Yee Cheng Chin, closes #11274)
diff --git a/src/getchar.c b/src/getchar.c
index 10f7f0e..d1d3fc6 100644
--- a/src/getchar.c
+++ b/src/getchar.c
@@ -2326,6 +2326,10 @@
 # ifdef FEAT_TERMINAL
 	free_unused_terminals();
 # endif
+
+# ifdef FEAT_SOUND_MACOSX
+	process_cfrunloop();
+# endif
 # ifdef FEAT_SOUND_CANBERRA
 	if (has_sound_callback_in_queue())
 	    invoke_sound_callback();