gdk-pixbuf: support --universal

Signed-off-by: Adam Vandenberg <flangy@gmail.com>

Formula/gdk-pixbuf.rb

@@ -5,20 +5,25 @@ class GdkPixbuf < Formula
   url 'http://ftp.gnome.org/pub/GNOME/sources/gdk-pixbuf/2.24/gdk-pixbuf-2.24.0.tar.bz2'
   sha256 '38d2630314e6d91976bffd833236f84fefa440a9038f86dc422820a39f2e3700'
 
+  depends_on 'pkg-config' => :build
   depends_on 'glib'
   depends_on 'jasper'
   depends_on 'libtiff'
 
+  def options
+    [["--universal", "Build a universal binary."]]
+  end
+
   def install
-    args = ["--prefix=#{prefix}",
-            "--disable-dependency-tracking",
+    ENV.universal_binary if ARGV.build_universal?
+    system "./configure", "--disable-dependency-tracking",
                           "--disable-maintainer-mode",
                           "--enable-debug=no",
+                          "--prefix=#{prefix}",
                           "--with-libjasper",
                           "--enable-introspection=no",
                           "--disable-Bsymbolic",
-            "--without-gdiplus"]
-    system "./configure", *args
+                          "--without-gdiplus"
     system "make"
     system "make install"
   end