hiera-eyaml: simplify

pkgs/tools/system/hiera-eyaml/default.nix

@@ -1,22 +1,9 @@
-{ lib, bundlerEnv, stdenv }:
+{ lib, bundlerEnv, ruby }:
 
-let
-  name = "hiera-eyaml-${env.gems.hiera-eyaml.version}";
-
-  env = bundlerEnv {
-    inherit name;
-    gemfile = ./Gemfile;
-    lockfile = ./Gemfile.lock;
-    gemset = ./gemset.nix;
-  };
-
-in stdenv.mkDerivation {
-  inherit name;
-
-  buildCommand = ''
-    mkdir -p $out/bin
-    ln -s ${env}/bin/eyaml $out/bin/eyaml
-  '';
+bundlerEnv {
+  inherit ruby;
+  pName = "hiera-eyaml";
+  gemdir = ./.;
 
   meta = with lib; {
     description = "Per-value asymmetric encryption of sensitive data for Hiera";