ruby: patch path in tzdata gem

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

@@ -19,7 +19,7 @@
 
 { lib, fetchurl, writeScript, ruby, libxml2, libxslt, python, stdenv, which
 , libiconv, postgresql, v8, v8_3_16_14, clang, sqlite, zlib, imagemagick, pkgconfig
-, ncurses, xapian, gpgme, utillinux, fetchpatch
+, ncurses, xapian, gpgme, utillinux, fetchpatch, tzdata
 }:
 
 let
@@ -103,6 +103,13 @@ in
     ];
   };
 
+  tzdata = attrs: {
+    postPatch = ''
+      substituteInPlace lib/tzinfo/zoneinfo_data_source.rb \
+        --replace "/etc/zoneinfo" "${tzdata}/share/zoneinfo"
+    '';
+  };
+
   xapian-ruby = attrs: {
     # use the system xapian
     buildInputs = [ xapian pkgconfig zlib ];