Create Dockerfile for building nginx x64 for windows

> We currently need to build nginx for x64. Do we have steps for that process and do they belong in this repo?

Somehow, I missed this question. :) The steps to build nginx x64 was similar to this: http://nginx.org/en/docs/howto_build_on_win32.html . You'd have to make sure that all your dependencies are x64, for the most part. I tried to create a ``Dockerfile`` for it, so anyone can easily build that image, but I was missing ``nmake`` / ``vcvarsall.bat``, so I couldn't finish it, and I didn't have enough time find a solution for that. :)

_Originally posted by @claudiubelu in https://github.com/kubernetes-sigs/windows-testing/issues/255#issuecomment-804411668_

If we need to make updates for any reason we need to be able to build the images referenced at https://github.com/kubernetes/kubernetes/blob/1a983bb958ba663e5d86983c55a187fb8c429c51/test/images/nginx/Dockerfile_windows#L19

This dockerfile should live in https://github.com/kubernetes/kubernetes/tree/master/test/images/windows

Start with the nginx Windows build guide and the referenced Kubernetes test/images/nginx/Dockerfile, then inspect the proposed destination in kubernetes/test/images/windows. Determine how the Dockerfile can provide the x64 build dependencies, including nmake and vcvarsall.bat; done means the referenced Windows nginx image can be built and updated from this repository.

Written by the indexing model from the issue text.