Make ninja smart console builds more pretty
Summary: CMake's find_package outputs to the console on success, which confuses the smart console mode of the ninja build system. Let's quiet the success message and manually warn instead.
Reviewers: tstellar, phosek, mehdi_amini
Reviewed By: mehdi_amini
Subscribers: mgorny, llvm-commits
Differential Revision: https://reviews.llvm.org/D82276