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

[via llvm-commits]

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

If I'm not mistaken, it still reports the warning somewhere, therefore I left the warning message here since it's the only place where we check for double definitions.

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