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