[PATCH] Windows ToolChain: remove excessive backslash if we find WindowsSDK

[Yaron Keren]

  I 'm not sure the problem is here. The sys::path::append function knows how to deal with duplicate slashes so if you do get duplicate backslash, plain string concatenation was probably used instead of sys::path::append. In such case the correct bug fix would be to use sys::path::append instead of the string concatenation.

http://reviews.llvm.org/D3440