Use system/libcppbor if available am: 14d4bbc051

Original change: https://android-review.googlesource.com/c/trusty/app/keymaster/+/2736441

Change-Id: If19d3e67effca7b1a76c906f911e32200f99eb59
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>