add workaround to tarball without root

[EduardoRFS]

This is the same behavior as tar --strip-components IIRC. Also it's needed to build @opam/hacl-star-raw. This also enables Tezos to be build using esy

[ManasJayanth]

Shouldnt one of the roots be followed atleast?

      | [h, ...tail]=>
        let%lwt () = Logs_lwt.info(m => m("warning: multiple root dirs found. "));
        find(h, n - 1)

[EduardoRFS]

Nope, multiple roots, means that there is multiple files in the root, most of the time that implies that the tarball doesn't have a wrapping folder, as you can see on

https://github.com/project-everest/hacl-star/releases/download/ocaml-v0.3.0/hacl-star.0.3.0.tar.gz