check-clang-tools: Fixup for r199583.

  - Forgot to tweak autoconf's Makefile.
  - Apply lit's param to config.clang_tools_dir.

git-svn-id: https://llvm.org/svn/llvm-project/clang-tools-extra/trunk@199589 91177308-0d34-0410-b5e6-96231b3b80d8