Setup zstd in build_helper
Setup zstd in build_helper

Summary:
Right now ubuntu build fails on folly dependency on newer zstd lib than is provided by distro.
Adding setup_zstd to clone and build zstd, similar to other dependencies.

Reviewed By: lnicco

Differential Revision: D26692582

fbshipit-source-id: bd7514cbf3e40271b25658fc543e6dc3d3c8b2ee

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