[llvm] [WebAssemblyLowerEmscriptenEHSjLj] Avoid setting import_name where possible (PR #128564)

[Sam Clegg via llvm-commits]

sbc100 wrote:

Thanks for pointing out 296ccef.  I think I will use the to make this PR more explict.

https://github.com/llvm/llvm-project/pull/128564