bundlerEnv: always include default gems

"default" isn't really a group, it's more the absence of one. With
Bundler, this means that a gem should be installed unconditionally,
regardless of which groups are specified. It doesn't really make sense
to allow these gems to be omitted from a bundlerEnv.

pkgs/development/ruby-modules/bundled-common/functions.nix

@@ -52,7 +52,7 @@ in rec {
 
   groupMatches = groups: attrs:
     groups == null || !(attrs ? "groups") ||
-      (intersectLists groups attrs.groups) != [];
+      (intersectLists (groups ++ [ "default" ]) attrs.groups) != [];
 
   applyGemConfigs = attrs:
     (if gemConfig ? "${attrs.gemName}"