build, tools, win: add .S files support to GYP

Makes GYP properly handle .S files.

Fixes: https://github.com/nodejs/node-v8/issues/89

PR-URL: https://github.com/nodejs/node/pull/24553


Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>