Upgrade the 'stack' script to python3.

Also hook up the test to Android.bp.

Test: unit test
Test: Ran with a tombstone file as parameter.
Test: Ran pasting in stack to stdin.
Change-Id: I25f40569cc49b7487553611bcc25d061179bfa8d

scripts/example_crashes.py

@@ -1,5 +1,3 @@
-#!/usr/bin/env python
-#
 # Copyright (C) 2014 The Android Open Source Project
 #
 # Licensed under the Apache License, Version 2.0 (the "License");