Summary: When you compile with COMPILE_WITH_TSAN=1, we will compile the code with -fsanitize=thread. This will resolve bunch of data race issues we might have.

Test Plan: COMPILE_WITH_TSAN=1 m db_test

Reviewers: yhchiang, rven, sdong

Reviewed By: sdong

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D32019