I am not much concerned with hyper optimizations, but I was curious how OCaml would fair with the initial, simple steps, before things get crazy. But I opted for a more complex program:

    (\* t.ml \*)
    let () = print_endline "Hello, World!"

Then just doing a standard compilation and a strip:

    $ ocamlopt -o t t.ml && ls -l -h t | cut -d " " -f5
    1.5M
    $ strip t && ls -l -h t | cut -d " " -f5
    356K
    $ ./t
    Hello, World!

I may be overlooking something, and would be interested to learn what if so, but I was surprised we got a result smaller than the rust binary in the first instance.