[CMake] Support for Boost 1.70.0

[Stephan Menzel]

> On 12. Apr 2019, at 17:48, Michael Ellery <mellery451 at gmail.com> wrote:
> 
> oh, sorry I misunderstood. How did you build/install boost on windows

All ‘normal’ boostrap, build. With tagged filenames. Files look very much like I expect them to look. This will actually be the 50th boost version I’ll be using so I think I know the drill here. 

> I’m not sure what “Variable View” is…is that a CMake gui thing?

Yes. Didn’t know its official name. It does show all the libraries were found. 

>  Since it’s only complaining about a few libraries, is it possible that those three didn’t actually successfully build for one reason or another — maybe check the stage directory for the expected lib files (I believe you’d be looking for the “ -mt-x64.lib” files…)? If those files really are present, then I agree it’s a strange problem.

I also double checked this a few times. Even rebuilt Boost and tried with different files. 

I guess the answer really lies in ‘why those 3?’  At first I thought it would be dependencies among the imported targets but I did depend on them directly. Also, the error is thrown before I create any target myself, so it must be something about detecting if the libs are found or not. I‘m at a loss here. This is too strange. 

Cheers,
Stephan