cpp-api: WasmType/Val does not handle endianness conversions from native types on big-endian platforms

[leonm1]

The c-api indicates the values stored in wasmtime_val_raw_t indicate they must be little-endian.

For the cpp-api, passing native cpp types (such as uint32_t, uint64_t, etc) to wasmtime::WasmType does not perform the endianness conversion on big-endian platforms when storing directly into wasmtime_val_raw_t. I believe wasmtime::Val also needs endianness conversions.

Related: proxy-wasm/proxy-wasm-cpp-host#503 (comment)

[alexcrichton]

Thanks for the report! And yeah this is definitely a bug and would be good to fix!