[clang] Add nodelete annotation for WebKit checkers (PR #177839)

[Ryosuke Niwa via cfe-commits]

rniwa wrote:

> Looks harmless. I wonder what happens if you add this attribute but the function definition violates this. I suspect that such a mismatch wouldn't be detected, thus would remain in silence. Would that be possible/worth it to check this attribute if we have a definition? So that we could say, that this attribute needs to be in the header, but the implementation would also include this and check if it's in-sync with the definition. WDYT?

Yeah, I was thinking that it ought to be a new checker. Should I include it in this PR?

https://github.com/llvm/llvm-project/pull/177839