[clang] [clang][Sema] Deprecate `global`/`unknown` in `lifetime_capture_by` (PR #196635)

[Oliver Hunt via cfe-commits]

ojhunt wrote:

I’m not sure I buy the benefit of the explicit _this variant here - it seems to make many macro related things far harder, as has been mentioned it’s no longer possible to have simple availability macros, and certainly it makes life far harder for projects that have been adopting this at scale to have a breakage this severe and sudden - I get “experimental feature” but this is something that many projects have been adopting out of necessity

https://github.com/llvm/llvm-project/pull/196635