d6811208f4
If a system has LLVM installed, `find_package` could choose that one
even if we set `HIP_LLVM_ROOT`. `LLVM_ROOT` is ignored because of this
CMake policy is set to `OLD` by default.
Change-Id: I18fa0453afe170c229e92d6ddc386b43eb0c44f6
[ROCm/clr commit: a2a8dad980]