Driver: Change the driver to take the path to the main executable, instead of
taking it in pieces.
 - Fixes a problem where the Clang executable path was not initialized properly
   on Win32, because sys::Path::getBasename() doesn't do what I always think it
   does. Imagine that, a sys::Path interface that is confusing!

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@108667 91177308-0d34-0410-b5e6-96231b3b80d8
4 files changed