[CMake] Fix LLVM build non-determinism on RHEL

On RHEL, the OS tooling (ar, ranlib) is not deterministic by default.
Therefore, we cannot get bit-for-bit identical builds.

The goal of this patch is that it adds the flags required to force determinism.

Differential Revision: https://reviews.llvm.org/D64817

(cherry picked from commit c84c62c5)