build: change nosign flag to sign and flips logic

Makes the default build on Windows not try to sign the node.exe
binary after a build. Instead the 'sign' flag now indicates that the
binary should be signed. The 'nosign' flag is left as a noop.

Reviewed-By: Nikolai Vavilov <vvnicholas@gmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Bartosz Sosnowski <bartosz@janeasystems.com>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: João Reis <reis@janeasystems.com>
PR-URL: https://github.com/nodejs/node/pull/10156