While making lld build under the tools directory I decided to refactor how this
works.
There is now a macro, add_llvm_external_project, which takes the name of the
expected subdirectory. This sets up two CMake options.
* LLVM_EXTERNAL_${NAME}_SOURCE_DIR
This is the path to the source. It defaults to
${CMAKE_CURRENT_SOURCE_DIR}/${name}.
* LLVM_EXTERNAL_${NAME}_BUILD
Enable and disable building the tool as part of LLVM.
I chose LLVM_EXTERNAL_${NAME} as a prefix so they all show up together in the
GUI.
llvm-svn: 155654