[lld] wasm-ld: Add allow-multiple-definition flag (PR #97699)

[via llvm-commits]

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@@ -310,9 +310,14 @@ static bool shouldReplace(const Symbol *existing, InputFile *newFile,
   }
 
   // Neither symbol is week. They conflict.
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mzukovec wrote:

I see that ELF has some checks with `errorOrWarn`; duplicated symbols are one of them. Would you like me to do the same for `wasm-ld`? In that case, I may need some help with other checks, which may be non-breaking in case of a warning.

https://github.com/llvm/llvm-project/pull/97699