Avoid hardcoding the path of wasi-sdk in wamr_toolchain.cmake, allow passing -w [wasi-sdk path] to build_sdk.sh, allow passing OUT_DIR to app-sdk and runtime-sdk, and optimize message information.
Avoid hardcoding the path of wasi-sdk in wamr_toolchain.cmake, allow passing -w [wasi-sdk path] to build_sdk.sh, allow passing OUT_DIR to app-sdk and runtime-sdk, and optimize message information.