Reapply SVN r274797.

Original Commit Message

    Driver: Stop linking to C++ when using sanitizers on Darwin

    Sanitizers on Darwin are built as dynamic libraries, not static libraries.
    Sanitizers will have their C++ dependency satisfied internally (LC_LOAD_DYLIB)
    in the libclang_rt dylib. As long as the sanitizers stay dynamic and not static,
    linking against C++ when enabling a sanitizer becomes over linkage.

    Patch by Dave Lee!

llvm-svn: 275032