metasploit-framework: fix build

> /nix/store/r2vsi140pys7jnzyk0qz1fj9aji6sq40-ruby2.5.3-rb-readline-0.5.5/lib/ruby/gems/2.5.0/gems/rb-readline-0.5.5/lib/rbreadline.rb:1097:in `<module:RbReadline>': HOME environment variable (or HOMEDRIVE and HOMEPATH) must be set and point to a directory (RuntimeError)

pkgs/development/ruby-modules/gem-config/default.nix

@@ -226,6 +226,12 @@ in
     '';
   };
 
+  metasploit-framework = attrs: {
+    preInstall = ''
+      export HOME=$TMPDIR
+    '';
+  };
+
   msgpack = attrs: {
     buildInputs = [ msgpack ];
   };