Summary:
From bzip2's official [download page](http://www.bzip.org/downloads.html), we could download it from sourceforge. This source would be more credible than previous web archive.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5995

Differential Revision: D18377662

fbshipit-source-id: e8353f83d5d6ea6067f78208b7bfb7f0d5b49c05