Removing some left over from eng/Build.props and add a comment explaning why we need to select the solution to build.
Removing some left over from eng/Build.props and add a comment explaning why we need to select the solution to build.

mono/msbuild,jeffkl/msbuild,AndyGerlicher/msbuild,mono/msbuild,cdmihai/msbuild,AndyGerlicher/msbuild,mono/msbuild,cdmihai/msbuild,rainersigwald/msbuild,AndyGerlicher/msbuild,chipitsine/msbuild,AndyGerlicher/msbuild,sean-gilliam/msbuild,jeffkl/msbuild,cdmihai/msbuild,cdmihai/msbuild,sean-gilliam/msbuild,sean-gilliam/msbuild,Microsoft/msbuild,mono/msbuild,jeffkl/msbuild,Microsoft/msbuild,sean-gilliam/msbuild,chipitsine/msbuild,jeffkl/msbuild,Microsoft/msbuild,Microsoft/msbuild,rainersigwald/msbuild,rainersigwald/msbuild,rainersigwald/msbuild,chipitsine/msbuild,chipitsine/msbuild