[llvm] Fix warnings while building llvm against emscripten for web assembly (PR #118262)

[Anutosh Bhat via llvm-commits]

anutosh491 wrote:

I mean I've seen people build it with warnings. The recipe hosted on emscripten-forge also has warnings but just ignores it. I just thought of addressing it here.

https://github.com/llvm/llvm-project/pull/118262