[clang] [Clang] Add diagnostic about "%P" specifier with Objective-C pointers (#89968) (PR #89977)

[Jared Grubb via cfe-commits]

jaredgrubb wrote:

Cc: @ahatanaka @egorzhdan
Also cc @joker-eph as it looks like you were original author of some of this, in case you're still following it :)

https://github.com/llvm/llvm-project/pull/89977