ANDROID: GKI: Build INCREMENTAL_FS into GKI

For GKI 2.0, build incremental into the GKI image. This allows various
internal symbols to be hidden from modules again.

Bug: 133435829
Signed-off-by: Alistair Delva <adelva@google.com>
Change-Id: Ie8f6cdbd7eeff8e97b25312ba893cc49483dc346