build: exclude npm test directories on Windows

npm test directories are excluded on other platforms by
`tools/install.py`. Do the same on Windows.

Fixes: https://github.com/nodejs/node/issues/22901

PR-URL: https://github.com/nodejs/node/pull/23001


Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: João Reis <reis@janeasystems.com>