[clang-rename] Use add_clang_tool

`add_clang_tool` includes a call to `add_clang_executable`, but it also
sets up the install rule, and adds an `install-*` target. The latter is
required for using `LLVM_DISTRIBUTION_COMPONENTS`.

Differential Revision: https://reviews.llvm.org/D39522

llvm-svn: 317150