[CMake] simplest possible NSIS package

[John Drescher]

> Just to make you laugh I found the source of the problem.
> Apparently if you try to run an installer from a directory which is on a
> shared directory (with the virtualbox
> sharing) it just won't run :D
>
> Copying it somewhere else works perfectly, quite amazing issue.
>

Thanks for reporting back. That was very puzzling to me since my NSIS
builds have worked for a long time.

John