Add rt and perl packages it needs

pkgs/servers/rt/default.nix

@@ -0,0 +1,23 @@
+{ stdenv, fetchurl, perl }:
+
+stdenv.mkDerivation rec {
+  name = "rt-4.2.12";
+
+  src = fetchurl {
+    url = "https://download.bestpractical.com/pub/rt/release/${name}.tar.gz";
+
+    sha256 = "0r3jhgfwwhhk654zag42mrai85yrliw9sc0kgabwjvbh173204p2";
+  };
+
+  patches = [ ./override-generated.patch ];
+
+  buildInputs = [ perl ];
+
+  buildPhase = "true";
+
+  installPhase = ''
+    mkdir $out
+    cp -a {bin,docs,etc,lib,sbin,share} $out
+    find $out -name '*.in' -exec rm '{}' \;
+  '';
+}

pkgs/servers/rt/override-generated.patch

@@ -0,0 +1,21 @@
+commit 7aec1e9478ef679227e759ab9537df7584c6a852
+Author: Shea Levy <shea@shealevy.com>
+Date:   Fri Jan 15 09:09:18 2016 -0500
+
+    Make it possible to override hard-coded paths
+
+diff --git a/lib/RT/Generated.pm.in b/lib/RT/Generated.pm.in
+index 9dcb80b..99b034b 100644
+--- a/lib/RT/Generated.pm.in
++++ b/lib/RT/Generated.pm.in
+@@ -82,4 +82,10 @@ $MasonDataDir = '@MASON_DATA_PATH@';
+ $MasonSessionDir = '@MASON_SESSION_PATH@';
+ 
+ 
++if ( my $override_file = $ENV{RT_PATHS_OVERRIDE} )
++{
++    require "$override_file" || die "Couldn't load paths override file: $@";
++}
++
++
+ 1;