[clang] [llvm] [WebAssembly] Add support for nonnull_extern_ref type (PR #148935)

[Paulo Matos via cfe-commits]

pmatos wrote:

Sorry for the delay on coming back to this. I will take another look and help @badumbatish make progress here.

@dschuff fyi, @badumbatish is with Igalia and I will internally provide any help she needs to make progress here.

https://github.com/llvm/llvm-project/pull/148935