[build2] build2 0.6.2 bootstrapping broken with update 5 of VS 2017

[Boris Kolpackov]

Gerardo Hernandez <gerardohcampos at gmail.com> writes:

> The build2 bootstrapping is broken cause _MSC_VER has increased to 1912 in
> Visual Studio 2017 update 5, [...]
> 
> I have attached the patch to solve it, but unfortunately I reckon some
> packages in cppget.org will need updating as well.

Thanks for the report and the patch. I've actually added support for 15u5
in master a couple of days ago (there are some more bits required). If you
grab the latest stage, everything should work[1]:

https://stage.build2.org/0/

[1] https://stage.build2.org/?builds=&cf=windows_10-msvc_15u5

Boris