Summary: Some test and benchmark codes don't build for CYGWIN. Fix it.

Test Plan: Build "make all" with TARGET_OS=Cygwin on cygwin and make sure it passes.

Reviewers: rven, yhchiang, anthony, igor, kradhakrishnan

Reviewed By: igor, kradhakrishnan

Subscribers: leveldb, dhruba

Differential Revision: https://reviews.facebook.net/D39711