update timestamp of mirrored fcp files when copying them over so that make knows they are up to date
update timestamp of mirrored fcp files when copying them over so that make knows they are up to date

Summary: Kept seeing those being installed despite not changing.

Reviewed By: jberdine

Differential Revision: D4455398

fbshipit-source-id: f125bcd

ryoon/infer,ryoon/infer,jvillard/infer,ropas/infer,jvillard/infer,blzq/infer,facebook/infer,facebook/infer,jsachs/infer,jvillard/infer,ryoon/infer,jsachs/infer,ropas/infer,blzq/infer,ropas/infer,facebook/infer,ropas/infer,jsachs/infer,jvillard/infer,jvillard/infer,blzq/infer,ropas/infer,ropas/infer,jsachs/infer,facebook/infer,ryoon/infer,ryoon/infer,blzq/infer,ryoon/infer,facebook/infer,jsachs/infer,facebook/infer,blzq/infer,facebook/infer,jsachs/infer,jvillard/infer,blzq/infer,jvillard/infer