Motivation for this change

Dependency for dune-release which I am working on packaging. Used a unstable version, since the last release's jbuilder setup seems broken by now and the old API isn't broken.

I decided to patch in a static path to curl, since curly assumes that it'll find curl in PATH by default, which is kind of hard to ensure for a library. The static path can still be overridden by the user of the library if they want to, however.

Another solution to the problem could be to not care about it in curly, but use wrapProgram for all user applications that use curly and add curl to PATH there. I think doing it in curly is nicer overall and should ensure that it works out of the box, but let me know what you think!

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS linux)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Determined the impact on package closure size (by running nix path-info -S before and after)
• Ensured that relevant documentation is up to date
• Fits CONTRIBUTING.md.