shift to a single package for selecting cross-target

[avsm]

I've successfully got this cross-compiling some binaries to my raspberry pi, from my mac now! I experimented with a different layout here to make it easier to add targets, added here as a draft PR to show you:

• conf-zig-cross configures the zig_triple and ocaml_triple opam variables. There are multiple versions of this package depending on your target (conf-zig-cross.rpi or conf-zig-cross.x86_64-al2023 for example)
• conf-zig-wrapper installs the wrapper scripts, after querying conf-zig-cross
• zig-ocaml-cross installs the cross toolchain as cross-sysroot querying conf-zig-cross

With this I can now do:

opam install conf-zig-cross.rpi zig-ocaml-cross to get the rpi cross compiler, and then use the zig-cross-* wrappers to set CC/CXX/etc in my C library Makefile to do a full cross compile. The dune command is dune build -p rgb_matrix -x cross.

[chris-armstrong]

Thanks @avsm . Can I ask if you've tried this layout with dependencies? I started with something like this but ran into problems quickly with it

[avsm]

Not yet, it’s very lightly tested. I’m going to try getting Core working when I get a chance this week. I’d like to aim for something more usable than renaming all the opam packages with the target suffix; there’s a got to be a more elegant way! (But i have no idea what yet, many have tried…)