Use String8/16 c_str am: 0e78ec20b9

Original change: https://android-review.googlesource.com/c/platform/system/update_engine/+/2705913

Change-Id: I1ad3080dff46c17f70cb3a1e32c8e9c56cb1dffa
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>