Summary:
X-link: https://github.com/facebookexternal/rdma_gen/pull/17

Findibverbs.cmake found the library, but we want to require a recent one
and fail if that is not present.  If pkg-config doesn't know the version,
we fall back to figuring it out from the name of the .so file.

Reviewed By: ahornby

Differential Revision: D88577550

fbshipit-source-id: dc32140f9786a1af4739656468e5c08ffde6ae36