emacs: Build cocoa on darwin

pkgs/applications/editors/emacs-24/default.nix

@@ -50,7 +50,9 @@ stdenv.mkDerivation rec {
     ++ stdenv.lib.optional (stdenv.isDarwin && withX) cairo;
 
   configureFlags =
-    if withX
+    if stdenv.isDarwin
+      then [ "--with-ns" "--disable-ns-self-contained" ]
+    else if withX
       then [ "--with-x-toolkit=${toolkit}" "--with-xft" ]
       else [ "--with-x=no" "--with-xpm=no" "--with-jpeg=no" "--with-png=no"
              "--with-gif=no" "--with-tiff=no" ];
@@ -61,6 +63,9 @@ stdenv.mkDerivation rec {
   postInstall = ''
     mkdir -p $out/share/emacs/site-lisp/
     cp ${./site-start.el} $out/share/emacs/site-lisp/site-start.el
+  '' + stdenv.lib.optionalString stdenv.isDarwin ''
+    mkdir -p $out/Applications
+    mv nextstep/Emacs.app $out/Applications
   '';
 
   doCheck = true;