Fix the clang -Werror build after r217152 by flagging a polymorphically used but statically owned hierarchy with a protected base dtor and final classes to satisfy -Wnon-virtual-dtor

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@217167 91177308-0d34-0410-b5e6-96231b3b80d8