Summary:
For internal build enviroment only. Developer could run the
microbenchmark without `ROCKSDB_NO_FBCODE=1`.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/8954
Test Plan: `$ make microbench` on dev server
Reviewed By: ajkr
Differential Revision: D31163717
Pulled By: jay-zhuang
fbshipit-source-id: 1ff59f660ca05afd0fd5c7c7dcdfd831ac365462