[analyzer] scan-build for Windows

The patch allows Windows users to launch scan-build without any additional preparations in the same way as it described in http://clang-analyzer.llvm.org/scan-build.html. The only thing that should be done to make scan-build work from an arbitrary location is to add scan-build folder to the PATH environment variable.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@180900 91177308-0d34-0410-b5e6-96231b3b80d8