[Feature Request]: Support building CppInterOp with the wasm64-unknown-emscripten target

[mcbarton]

Description of new feature

I saw this issue in Emscripten forge emscripten-forge/recipes#3021 that suggests there is appetite for wasm64 builds as well as wasm32. Its not clear how difficult this would be to support, but when I switched the llvm target and used the necessary emscripten flag (at least the only one I know of) llvm would not build (I forget the exact message, but it errors about something being ambiguous)