Install clang-format-linter Arcanist library on devserver role

Summary:
Needed by rabbitmq-tcl, per 283a03d7.

On FreeBSD, several clang/llvm versions can coexist,
so there is a need to create clang-format alias.

Test Plan: arc lint

Reviewers: dereckson

Reviewed By: dereckson

Differential Revision: https://devcentral.nasqueron.org/D3064