[clang] [clang] Disable missing definition warning on pure virtual functions (PR #74510)

[Charalampos Mitrodimas via cfe-commits]

charmitro wrote:

> Perhaps needs a release note.

> Can you add a release note indicating #74016 was fixed? Otherwise LGTM.

Release note added.

> If you wanted to make a follow up {R to rename `isPure` to `isPureVirtual`, i think that might be helpful (to avoid confusion with the `gnu::pure` attribute)

Yes, this could be helpful. I'll create a follow up PR for this.


https://github.com/llvm/llvm-project/pull/74510