gio: Fix build on OS X < 10.9
gio: Fix build on OS X < 10.9

Commit 170466db accidentally partially reverted commit d1a03bc7.
Reinstate the missing check for OS X 10.9.

The Meson build does not have this problem.

https://bugzilla.gnome.org/show_bug.cgi?id=794380

endlessm/glib,endlessm/glib,endlessm/glib,endlessm/glib,endlessm/glib