update engine: fix gnu++20 build am: 95bc6fb2c8

Original change: https://android-review.googlesource.com/c/platform/system/update_engine/+/2834790

Change-Id: I285eed2d3c4c65401a33cc6643690ef66ca78f82
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>