I have followed your steps and it it working fine locally. i can run hello_wasi_http.wasm on my local machine with below command.
wasmtime serve /hello_wasi_http.wasm

I have configured minikube cluster with wasmtime runtime. for normal helloworld below OCI image is working fine.

FROM scratch
ADD hello-wasm.wasm /
CMD ["/hello-wasm.wasm"]

but now i want to build image with http serve. then how can I define docker file with serve?

FROM scratch

Add the Wasm file to the container

ADD hello_wasi_http.wasm /hello_wasi_http.wasm

Expose port 8080

EXPOSE 8080

Start the Wasmtime server

CMD ["wasmtime", "serve", "/hello_wasi_http.wasm"]

i tried this one but not working. can you please tell how can I access http server ?