[clang] [clang] Refactor target attribute mangling. (PR #81893)

[Alexandros Lamprineas via cfe-commits]

labrinea wrote:

> > I wonder if this should be a part of the Targets in CodeGen instead of here?
> 
> Hrm, this is a bad idea as the rest of mangling is in AST, but having mangling outside of AST seems to be the problem here.

I could move the logic under ABIInfo which is already referencing AST. Overrides of ABIInfo are provided in CodeGen/Targets as you suggested. It doesn't seem a bad idea to me.

https://github.com/llvm/llvm-project/pull/81893