Summary:
simply enable the macro in internal build, it wont hurt other sanitizers and will fix UBSAN issues
Closes https://github.com/facebook/rocksdb/pull/2625

Differential Revision: D5475897

Pulled By: IslamAbdelRahman

fbshipit-source-id: 262c6fd5de3c1906f4b29e55b39110f125f41057