#2517 setup: prefer the cmake/ninja in venv over one on regular PATH

Beschreibung

## Summary
find_tool used the first cmake on PATH that ran, so if the user already had cmake installed, it'd use that even though setup pip-installs its own into .venv, which can cause problems if it's not a compatible version.

## What changed
Check for a binary in the local venv Scripts/ folder before checking trying `which`