How to use my custom clang to build Project

Environment : UE 4.14 , OS X 10.10.5

Hi, all !

I Have a question about build Unreal Game project.
i have custom clang, i want use this clang when build game project.

i changed the clang in /Users/Shared/Epic Games/UE_4.14/Engine/Extras/ThirdPartyNotUE/emsdk/Mac/clang/incoming to what i created.

but its still use original clang…

how can i change to my clang?