[PATCH] D77740: [CMake] Add a warning message to prepare the upcoming upgrade to CMake 3.13.4

[Fangrui Song via Phabricator via llvm-commits]

MaskRay added a comment.

Second to what jyknight has said.

> Add a warning like this -- but saying the minimum will be upgraded SOON, not in 11.0.0.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D77740/new/

https://reviews.llvm.org/D77740