dhallPackages: add recurseIntoAttrs
dhallPackages: add recurseIntoAttrs

dhallPackages were not built by the hydra, because the
`recurseIntoAttrs` calls was missing (all other package sets use it to
make hydra build the packages).

NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs