[Patch 1/2][ipa] Add target hook to sanitize cloned declaration's attributes

[Jan Hubicka]

> Hi,
> 
> I have changed the name to make the target hook more general and not create
> the illusion it is related to sanitizers.
> 
> Is this OK for trunk?
Can't you just go via IPA symbol summary or add_cgraph_duplication_hook?

Honza