upgrade clang plugin (clang/setup.sh improvement)
upgrade clang plugin (clang/setup.sh improvement)

Reviewed By: ryanrhee

Differential Revision: D4627973

fbshipit-source-id: 523a227

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