Motivation for this change

Indilib upstream recently moved many of their astronomical equipment drivers to a separate repository that is built and linked against the core project. Since indi clients use XML files in $prefix/share/indi/ to discover what drivers are available on the system, a buildEnv wrapper to combine the indi core with arbitrary 3rd party drivers is necessary. This provides the framework for users to override indilib in other derivations to support their devices.

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.