gobject-introspection: Fix variable override order

The DEPENDS variable override ordering here was almostly certainly
incorrect and led to weird behaviour when making changes elsewhere.
Correct it.

(From OE-Core rev: c8f7e922)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
(cherry picked from commit 3a59f2abe2713151f429d50a96e2360598fd30df)
Signed-off-by: Anuj Mittal <anuj.mittal@intel.com>