[clang] [clang] Allow devirtualisation of indirect calls to final virtual methods (PR #165341)

[Oliver Hunt via cfe-commits]

ojhunt wrote:

> > > BTW, have you tested it with bootstrapped build?
> > 
> > 
> > no, but honestly my success rate at simply getting a trivial bootstrap build to work has not been great :-/
> 
> I can try to make it.

got a stage2 build actually working, and am running tests atm

https://github.com/llvm/llvm-project/pull/165341