[llvm] WebAssembly: Move runtime libcall setting out of TargetLowering (PR #142624)

[Sam Clegg via llvm-commits]

sbc100 wrote:

> RuntimeLibcallInfo needs to be correct outside of codegen contexts.

Can you explain why?

I see other calls to setLibcallName that are happening in ISelLowering.cpp file:

e.g. 

```
llvm/lib/Target/X86/X86ISelLowering.cpp:    setLibcallName(RTLIB::UNWIND_RESUME, "_Unwind_SjLj_Resume");
```

Are all of these wrong too?

https://github.com/llvm/llvm-project/pull/142624