GNUtoMS: Fix for VS2017
This patch adds in a semi-hardcoded query to the VS2017 installer using cmake_host_system_information(). It also contains some future-proofing comments to make continuing to keep up with VS major releases easier. This assumes that their install location and path has somewhat permanently transitioned to the VS2017 installer for 2017+ versions one day.
Topic-rename: vs15-GNUtoMS