built with CommandLine.h will want the --version option to report that the
tool belongs to LLVM. To override simply pass a void func() to the
cl::SetVersionPrinter() function and that void func() will be called when
it is time to print the version information.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@28687 91177308-0d34-0410-b5e6-96231b3b80d8