[llvm] [CMake] enable CMP0144 policy if available (PR #96589)

[Fabian Mora via llvm-commits]

fabianmcg wrote:

@MaskRay are the warnings being caused by `mlir/lib/Target/LLVM/CMakeLists.txt`?
Because AFAICT `mlir/lib/Target/LLVM/CMakeLists.txt` is not really affected by the change of policy because the `*_ROOT` variable in question is: `CUDAToolkit_LIBRARY_ROOT`, which is defined by `find_package(CUDAToolkit)` [(see `CUDAToolkit_LIBRARY_ROOT`)](https://cmake.org/cmake/help/latest/module/FindCUDAToolkit.html#result-variables) and not really a `<PACKAGENAME>_ROOT` variable.

https://github.com/llvm/llvm-project/pull/96589