disable closingTracked on OSX

Don't trust OSX FSEvents's eventFlagItemModified to be called when the last
writer of a file closes it; apparently that sometimes does not happen,
which prevented files from being quickly added.

This commit was sponsored by John Peloquin on Patreon.

Utility/DirWatcher.hs

@@ -64,18 +64,18 @@ eventsCoalesce = error "eventsCoalesce not defined"
 {- With inotify, file closing is tracked to some extent, so an add event
  - will always be received for a file once its writer closes it, and
  - (typically) not before. This may mean multiple add events for the same file.
- - 
- - fsevents behaves similarly, although different event types are used for
- - creating and modification of the file.
  -
  - OTOH, with kqueue, add events will often be received while a file is
  - still being written to, and then no add event will be received once the
- - writer closes it. -}
+ - writer closes it.
+ - 
+ - fsevents sometimes behaves similarly, but has sometimes been 
+ - seen to behave like kqueue. -}
 closingTracked :: Bool
-#if (WITH_INOTIFY || WITH_FSEVENTS || WITH_WIN32NOTIFY)
+#if (WITH_INOTIFY || WITH_WIN32NOTIFY)
 closingTracked = True
 #else
-#if WITH_KQUEUE
+#if (WITH_KQUEUE || WITH_FSEVENTS)
 closingTracked = False
 #else
 closingTracked = error "closingTracked not defined"