clang/test/CMakeLists.txt: Prune CLANG_SOURCE_DIR and CLANG_BINARY_DIR. They are set at top.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@197575 91177308-0d34-0410-b5e6-96231b3b80d8
check-clang: Introduce clang_tools_dir in lit.site.cfg, for clang separated from llvm.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@197576 91177308-0d34-0410-b5e6-96231b3b80d8