Cross-compilling from MacOS to Linux. By default OCaml does dynamic linking of all C dependencies. Even with static linking there is a dependency on libc (or the MacOS equivalent) as far as I remember. I had some success so far with Rust, Nim and Go using a musl toolchain[1], but no luck for OCaml. At the moment I'm just using a docker container which mirrors the Debian distribution running on the Pi.

[1] https://github.com/messense/homebrew-macos-cross-toolchains