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

[Heejin Ahn via cfe-commits]

aheejin wrote:

> Yeah you've got it, that's the main point. It can be set via the C++ API, and when I tried doing so in the Rust compiler I found it broke the WebAssembly backend. Sorry if I didn't make that clear enough earlier, I'm glad we're on the same page now.

The other points I tried to say in https://github.com/llvm/llvm-project/pull/65876#issuecomment-1737922328 stay the same though.

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