[clang] [CodeGen][ObjC] Initial WebAssembly Support for GNUstep (PR #169043)

[Hugo Melder via cfe-commits]

hmelder wrote:

Given the complexity and current state, I think it makes sense to write a small design doc for the Objective-C Wasm EH support.

https://github.com/llvm/llvm-project/pull/169043