Add target to check for Windows SDK presence
Add target to check for Windows SDK presence

The Windows SDK plugin for Visual Studio adds a msbuild file that
represents a hidden dependency for the MSBuild build process.

Added a target early in the build process to check for the existence of
this file

rainersigwald/msbuild,mono/msbuild,sean-gilliam/msbuild,nikson/msbuild,ValMenn/msbuild,rainersigwald/msbuild,zima2219981998/msbuilding,chipitsine/msbuild,mono/msbuild,AndyGerlicher/msbuild,Microsoft/msbuild,ValMenn/msbuild,cdmihai/msbuild,Microsoft/msbuild,ValMenn/msbuild,mono/msbuild,jeffkl/msbuild,sean-gilliam/msbuild,Microsoft/msbuild,jeffkl/msbuild,chipitsine/msbuild,zima2219981998/msbuilding,rainersigwald/msbuild,jeffkl/msbuild,sean-gilliam/msbuild,cdmihai/msbuild,AndyGerlicher/msbuild,AndyGerlicher/msbuild,cdmihai/msbuild,jeffkl/msbuild,AndyGerlicher/msbuild,cdmihai/msbuild,Microsoft/msbuild,mono/msbuild,nikson/msbuild,chipitsine/msbuild,sean-gilliam/msbuild,rainersigwald/msbuild,nikson/msbuild,zima2219981998/msbuilding,nikson/msbuild,ValMenn/msbuild,chipitsine/msbuild