graphviz: partially use options dsl

Formula/graphviz.rb

@@ -9,6 +9,8 @@ class Graphviz < Formula
   url 'http://www.graphviz.org/pub/graphviz/stable/SOURCES/graphviz-2.28.0.tar.gz'
   sha1 '4725d88a13e071ee22e632de551d4a55ca08ee7d'
 
+  option :universal
+
   depends_on :libpng
 
   depends_on 'pkg-config' => :build
@@ -22,8 +24,7 @@ class Graphviz < Formula
   def options
     [
       ["--with-pangocairo", "Build with Pango/Cairo for alternate PDF output"],
-      ["--with[out]-bindings", "Build Perl/Python/Ruby/etc. bindings (default on Lion; may not work on earlier systems)"],
-      ['--universal', 'Build Graphviz with universal binaries and libraries']
+      ["--with[out]-bindings", "Build Perl/Python/Ruby/etc. bindings (default on Lion; may not work on earlier systems)"]
     ]
   end
 
@@ -33,7 +34,7 @@ class Graphviz < Formula
   end
 
   def install
-    ENV.universal_binary if ARGV.build_universal?
+    ENV.universal_binary if build.universal?
     args = ["--disable-debug",
             "--disable-dependency-tracking",
             "--prefix=#{prefix}",