src: allows escaping NODE_OPTIONS with backslashes

The characters specified within NODE_OPTIONS can now be escaped, which
is handy especially in conjunction with `--require` (where the file path
might happen to contain spaces that shouldn't cause the option to be
split into two).

Fixes: https://github.com/nodejs/node/issues/12971

PR-URL: https://github.com/nodejs/node/pull/24065


Reviewed-By: Anna Henningsen <anna@addaleax.net>