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/testdir/test_sound.vim b/src/testdir/test_sound.vim
index ff58262..e97ac61 100644
--- a/src/testdir/test_sound.vim
+++ b/src/testdir/test_sound.vim
@@ -17,7 +17,11 @@
   endif
   let g:playcallback_count = 0
   let g:id = 0
-  let id = 'bell'->sound_playevent('PlayCallback')
+  let event_name = 'bell'
+  if has('osx')
+      let event_name = 'Tink'
+  endif
+  let id = event_name->sound_playevent('PlayCallback')
   if id == 0
     throw 'Skipped: bell event not available'
   endif