[clang] [clang-tools-extra] [flang] [lld] [llvm] [flang][clang] Add Visibility specific help text for options (PR #81869)

[Andrzej Warzyński via cfe-commits]

https://github.com/banach-space commented:

+1

I've been thinking about something similar for a while now, but I've never had the cycles to try implementing it. Thanks for working on this! The OpenMP option is an excellent example for "why" to do this. I don't expect _that many_ options requiring this, but IMHO that's secondary. The "help" text should be accurate and this feels like the only way to achieve this. 

While you are here, I would consider looking into `DocBrief`. This one in particular:
* https://github.com/llvm/llvm-project/blob/main/clang/include/clang/Driver/Options.td#L851

That's another place that would benefit from something similar.

I'm a bit short on spare cycles for reviewing stuff :( @luporl , do you have time to go over this? I'll bump this on my list regardless.

https://github.com/llvm/llvm-project/pull/81869