getrusage harness for CacheLocality
getrusage harness for CacheLocality

Summary:
This diff adds unit tests that print out the wall, user, and
system time for two backend implementations of CacheLocality gathering.

Reviewed By: yfeldblum

Differential Revision: D16547404

fbshipit-source-id: 5b5467965eb21bc50ad7248c0badd814edc71d68

facebook/folly,facebook/folly,facebook/folly,facebook/folly,facebook/folly