Add contrib, 3rdparty to copy list for mock buildroot
Review Request #4379 - Created Nov. 15, 2016 and submitted
|kwlzn, nhoward_tw, yujiec|
Add contrib, 3rdparty to copy list for mock buildroot as v2 engine to pass prefix checks.
https://travis-ci.org/pantsbuild/pants/builds/176184104 (v2 engine on, shard 9 passed)
https://travis-ci.org/pantsbuild/pants/builds/176194952 (regular v1 run)