update_engine: use error_code for std::filesystem am: a77e645f14

Original change: https://android-review.googlesource.com/c/platform/system/update_engine/+/3217657

Change-Id: I5d7c3f5aa9f4bceace998667fe818eefece4deef
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>