[llvm] [lit] Migrate lit to ProcessPoolExecutor (PR #202681)

[via llvm-commits]

prasoon054 wrote:

Could you please check whether `psutil` is installed? The current implementation for cleaning up processes after "Ctrl+C" uses `psutil` to terminate the process tree on `SIGINT`.
See here: https://github.com/llvm/llvm-project/blob/2d12290550aca7e78a4575b4b09f75a3bc29576b/llvm/utils/lit/lit/util.py#L407


https://github.com/llvm/llvm-project/pull/202681