ruby: fixup mpdcron

pkgs/applications/networking/mailreaders/sup/.bundle/config

···
----
-BUNDLE_NO_INSTALL: true

pkgs/development/interpreters/ruby/bundler-env/default-gem-config.nix

···
       "--with-xslt-include=${libxslt}/include"
       "--with-exslt-lib=${libxslt}/lib"
       "--with-exslt-include=${libxslt}/include"
-      "--with-iconv-dir=${libiconv}"
-    ];
+    ] ++ lib.optional stdenv.isDarwin "--with-iconv-dir=${libiconv}";
   };
 
   pg = attrs: {

pkgs/tools/audio/mpdcron/Gemfile

···
+source "https://rubygems.org"
+gem "nokogiri"

pkgs/tools/audio/mpdcron/Gemfile.lock

···
+GEM
+  remote: https://rubygems.org/
+  specs:
+    mini_portile (0.6.2)
+    nokogiri (1.6.5)
+      mini_portile (~> 0.6.0)
+
+PLATFORMS
+  ruby
+
+DEPENDENCIES
+  nokogiri

pkgs/tools/audio/mpdcron/default.nix

···
 { stdenv, fetchgit, autoconf, automake, libtool, pkgconfig, glib, libdaemon, buildRubyGem
-, mpd_clientlib, curl, sqlite, ruby, rubyPackages, libnotify, pandoc }:
+, mpd_clientlib, curl, sqlite, ruby, bundlerEnv, libnotify, pandoc }:
 
-stdenv.mkDerivation rec {
+let
+  gemEnv = bundlerEnv {
+    name = "mpdcron-bundle";
+    gemfile = ./Gemfile;
+    lockfile = ./Gemfile.lock;
+    gemset = ./gemset.nix;
+  };
+in stdenv.mkDerivation rec {
   version = "20130809";
   name    = "mpdcron-${version}";
 
···
   };
 
   buildInputs =
-    [ autoconf automake libtool pkgconfig glib libdaemon haskellPackages.pandoc
-      mpd_clientlib curl sqlite ruby /*nokogiri*/ libnotify ];
+    [ autoconf automake libtool pkgconfig glib libdaemon pandoc
+      mpd_clientlib curl sqlite ruby gemEnv libnotify ];
 
   preConfigure = ''
     ./autogen.sh

pkgs/tools/audio/mpdcron/gemset.nix

···
+{
+  "mini_portile" = {
+    version = "0.6.2";
+    source = {
+      type = "gem";
+      sha256 = "0h3xinmacscrnkczq44s6pnhrp4nqma7k056x5wv5xixvf2wsq2w";
+    };
+  };
+  "nokogiri" = {
+    version = "1.6.5";
+    source = {
+      type = "gem";
+      sha256 = "1xmxz6fa0m4p7c7ngpgz6gjgv65lzz63dsf0b6vh7gs2fkiw8j7l";
+    };
+    dependencies = [
+      "mini_portile"
+    ];
+  };
+}