Use the final APK for dexpreopt when it's not stripped.

The final APK may contain compressed or uncompressed dex files,
and this affects dex2oat compilation.

Test: build sailfish, test that SystemUI.vdex and Settings.vdex
don't have the dex code.

Change-Id: Ic032f61ed67dcdf342f6eaef71d805b89d6fc99a