message: bazel: add note about running sanitizers on os x
diff: @@ -331,6 +331,12 @@ Similarly, for [thread sanitizer (TSAN)](https://github.com/google/sanitizers/wi
  bazel test -c dbg --config=clang-tsan //test/...
  ```
  +To run the sanitizers on OS X, prefix `macos-` to the config option, e.g.:
  +
  +```
  +bazel test -c dbg --config=macos-asan //test/...
  +```
  +
  ## Log Verbosity
  Log verbosity is controlled at runtime in all builds.
  