Implement preliminary OCaml support

[topolarity]

This is a preliminary implementation of OCaml compiler support in BinaryBuilder.

Dependent on JuliaPackaging/Yggdrasil#11146

[topolarity]

This looks to be almost working. There is some slight disagreement about darwinX in the target triples:

sandbox:${WORKSPACE}/srcdir # /opt/aarch64-apple-darwin/bin/ocamlopt.opt -v
The OCaml native-code compiler, version 5.4.0+dev2-2025-04-22
Standard library directory: /opt/aarch64-apple-darwin/bin/../lib/ocaml
sandbox:${WORKSPACE}/srcdir # ocamlopt.opt -v
/opt/bin/aarch64-apple-darwin20-libgfortran5-cxx11/ocamlopt.opt: line 5: /opt/aarch64-apple-darwin20/bin/ocamlopt.opt: No such file or directory

Any preference for how to resolve that?

[maleadt]

/opt/x86_64-linux-gnu/bin/../lib/gcc/x86_64-linux-gnu/5.2.0/../../../../x86_64-linux-gnu/bin/ld: /opt/x86_64-linux-gnu/bin/../lib/ocaml/stdlib.a(camlinternalFormatBasics.o): unrecognized relocation (0x2a) in section `.text.caml.camlCamlinternalFormatBasics$entry'
/opt/x86_64-linux-gnu/bin/../lib/gcc/x86_64-linux-gnu/5.2.0/../../../../x86_64-linux-gnu/bin/ld: final link failed: Bad value
collect2: error: ld returned 1 exit status

I guess this is because of using GCC 6 for building the shards (technically, OCaml only needs GCC 4.9+, but opam, one of the build tools I added to the shard, only builds on GCC 6 or later).