enable tests in getdeps
enable tests in getdeps

Summary: properly find the required GMock version (1.8.0) and allow building tests in getdeps

Reviewed By: mjoras

Differential Revision: D16935741

fbshipit-source-id: 46f62511e2feaf553d028e286a862aa5b30393c6

facebook/wangle,facebook/wangle,facebook/wangle