VisualStudioVersion not set correctly for portable projects

[ctaggart]

I compiled and included the latest open source MSBuild so that VisualStudioVersion would be set correctly when loading projects . Unfortunately, it appears that this solution may not be working for portable projects.

original problem: #50
original solution: http://blog.ctaggart.com/2015/05/sourcelinkmsbuild-uploaded-to-nuget.html

On AppVeyor it evaluated to 10.0:
fsprojects/FSharp.Data#852

On my computer it evaluated to 11.0:

In both cases, it should have been set to 12.0 for Visual Studio 2013.

The original work-a-round was to hardcode the setting to load:

let proj = VsProj.Load file ["Configuration","Release"; "VisualStudioVersion","12.0"]

Instead of:

let proj = VsProj.LoadRelease file

Another test work trying is commenting out Common.props.

<Import Project="$(MSBuildExtensionsPath)\$(MSBuildToolsVersion)\Microsoft.Common.props" Condition="Exists('$(MSBuildExtensionsPath)\$(MSBuildToolsVersion)\Microsoft.Common.props')" />

[ctaggart]

I filed this as dotnet/msbuild#122.

[ctaggart]

I'll upgrade MSBuild versions as they come out. Not much I can do about this.