fix Circle windows build
fix Circle windows build

Summary: Pull Request resolved: https://github.com/facebook/flow/pull/8572

Reviewed By: Hans-Halverson

Differential Revision: D25979717

fbshipit-source-id: 63c973d70f71811f7f7c396edd091f6c11538d7c

facebook/flow,facebook/flow,facebook/flow,facebook/flow,mroch/flow,mroch/flow,facebook/flow,facebook/flow,mroch/flow,mroch/flow,mroch/flow,mroch/flow,facebook/flow,mroch/flow