[clang] Allow direct dispatch for the ObjFW runtime >= 1.3 (PR #126382)

[Jonathan Schleifer via cfe-commits]

Midar wrote:

Copied the necessary parts from CGObjCMac to just ObjFW, as GNUstep decided to do it very differently.

Theoretically, the same could be done for the GCC runtime. Should it?

https://github.com/llvm/llvm-project/pull/126382