Allow giflib to be built unbundled

Change-Id: I229a3e2f606bac8021de513f0ee14afea86e74fc
am 621696a2: Add missing LOCAL_SDK_VERSION

* commit '621696a283c0ce34956417f760f1005fadcd12ae':
  Add missing LOCAL_SDK_VERSION
handle no content comment block in the gif.

Change-Id: I3c87a151b0d0f487865c4f84d26101797bc91290
Signed-off-by: Joey Pan <joey.pan@mediatek.com>
(cherry picked from commit 7ee131f83daab0744dbbfbbf2f375c05a5285f2e)