Revert r241621, "[CMake] Cleanup tools/CMakeLists.txt to take advantage of the auto-registration that was already partially working."

It broke the build that relies on LLVM_EXTERNAL_CLANG_*.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241663 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed