Use libunwindstack instead of libbacktrace. am: f44070ed04

Original change: https://android-review.googlesource.com/c/platform/art/+/2045667

Change-Id: I487cb9314fb7880aaed76633d3980750795c6461
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>