#1605 setup: skip a cmake/ninja on PATH that does not run, for the one next to this Python

Descripción

## Title
Issue: none filed.

## Summary
A cmake or ninja on `PATH` that does not run no longer fails every build; setup falls back to the one it installed
next to its Python.

## What changed
`setup.py` `find_tool` took the first `cmake`/`ninja` on `PATH` without running it. A pip-installed `ninja.exe` whose
Python had been removed was still on `PATH`; it is a launcher that fails at once, so every build failed, although
setup had just installed a working ninja in `.venv`. `find_tool` now runs the `PATH` tool with `--version` and, when
that fails, falls through to the one next to this Python.

## Extra Notes
Tested: on Windows with the broken launcher on `PATH`, the build used `.venv`'s ninja and finished;
`tools/test_setup_*.py` all pass.

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