Check external dex file checksum in `OatFile::Setup`. am: b33ae53da5 am: d28c908437

Original change: https://googleplex-android-review.googlesource.com/c/platform/art/+/17944312

Change-Id: If0ccfd6c9a0a45ac2143f4450b7a7503e4010f09
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>