Building darktable on Windows 10

Been a while since I studied or wrote/edited any C/C++. It would be interesting.

But - see below, why I’ll hold on this.

Until sigmoid gets included in the official dt roadmap, if periodically Jandren refreshes the sigmoid branch, (one or two months behind the bleeding edge version, is ok for me), then I can build from this revised branch, using the same process I followed earlier, and use this as my “dev” dt edition.

And yes, all warnings noted, installed in its own “dev” directory and own database/config directory, which I already adhere to, as directed by all the kind folks on pixls, with much thanks.