[clang] Ensure NoTrapAfterNoreturn is false for the wasm backend (PR #65876)

[Heejin Ahn via cfe-commits]

aheejin wrote:

> > But `--no-trap-after-noreturn` didn't exist before, so there was no way to specify that from the command line. You _created_ it, originally in this PR, and then the split-off PR in #67051. If this is a bugfix, it sounds like you are fixing a bug of your own making.
> 
> I think perhaps the misunderstanding here is that `NoTrapAfterNoreturn` was usable/settable by compilers such as rust via the LLVM API, even though `--no-trap-after-noreturn` didn't exist in llvm itself?
> 
> So adding this option allows us to test something that wasn't testable via the command line, but was exposed via the API? Is that right?

Ah, so it was already possible to set `NoTrapAfterNoreturn=0` via some API. I couldn't find one in the LLVM codebase that allowed it but I guess I don't know about Rust API part. Thanks for point that out, and sorry If I missed that. @majaha

https://github.com/llvm/llvm-project/pull/65876