ci: add an action to build binaries

[emillon]

This adds a manual workflow to get binaries for:

• linux (intel)
• mac (intel)
• mac (arm)

In addition, a combined zip is available.

[Leonidas-from-XIV]

Cool that nix can be used to deal with both OSes!

[anmonteiro]

I wonder if it'd be interesting to build a statically linked binary too, e.g. dune-musl64 on x86_64 linux.

I wonder if that'd allow distributing dune as a standalone binary, which could be especially useful for dune 4 and dune-pkg.

[emillon]

I wonder if that'd allow distributing dune as a standalone binary, which could be especially useful for dune 4 and dune-pkg.

I should have mentioned that, but yes that's the motivation behind that workflow: this way we can distribute binaries so that people can easily test that without installing anything else.

I wonder if it'd be interesting to build a statically linked binary too, e.g. dune-musl64 on x86_64 linux.

Sounds like a good idea, is there a "standard" way to do this with nix?

[anmonteiro]

Sounds like a good idea, is there a "standard" way to do this with nix?

It should be really easy with my overlays to build pkgsCross.musl64.ocaml-ng.ocamlPackages_4_14.dune.

[emillon]

done in #10485