[clang] Clang tooling generated visibility macros for Clang (PR #109702)

[Thomas Fransham via cfe-commits]

fsfod wrote:

> I'd like some answer about how we plan to ensure the macros remain correct. Short-term, "someone periodically runs the tool manually" might be good enough if we don't expect much churn, I guess.

Missing macros on some classes or functions shouldn't break any existing configurations or platforms while default symbol visibility is still left as public.

> Also, can the tool itself be added to llvm-project?

This is something i have been wondering about it wouldn't mind it being added, I just wasn't sure if it was too niche or not. I don't know if that was part of @compnerd 
original goal when he wrote it, I think he still on holiday atm.


https://github.com/llvm/llvm-project/pull/109702