build: vcbuild.bat fix for Visual Studio 2012

The commit adding support for VS2012 build (0602fbb49c159fe5eded343a0fbb447979d757ba ) does not work correctly, it generates project files in old format that is not supported by VS2012.

The new commit (0602fbb49c159fe5eded343a0fbb447979d757ba) fixes this problem.

/cc: @piscisaureus