Summary:
CircleCI is the new recommended CI system internally.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6518

Test Plan: Watch https://app.circleci.com/pipelines/github/facebook/rocksdb

Differential Revision: D20454743

Pulled By: cheng-chang

fbshipit-source-id: 39031568d6c1d3d25b7fbd78fa9a0e6067ddc47c