[llvm] [llvm-readtapi] Add install-distribution support (PR #67748)

[Cyndy Ishida via llvm-commits]

cyndyishida wrote:

> I see the usage of `add_llvm_tool_symlink` in other tools. Could that simplify the change?

I tried that initially. AFAICT it doesn't create a target, so I couldn't figure out how to get that symlink as a part of the installation step. I ended up doing a simpler version of https://github.com/llvm/llvm-project/blob/main/llvm-libgcc/CMakeLists.txt#L134 

https://github.com/llvm/llvm-project/pull/67748