gst-plugins-good: optional X11 dependency

Configure picks up X11 and tries to compile with it, but superenv
filters out the library paths during make; explicitly pass
--with/without-x to fix this.

Formula/gst-plugins-good.rb

@@ -25,6 +25,8 @@ class GstPluginsGood < Formula
   depends_on 'gst-plugins-base'
   depends_on 'libsoup'
 
+  depends_on :x11 => :optional
+
   # The set of optional dependencies is based on the intersection of
   # gst-plugins-good-0.10.30/REQUIREMENTS and Homebrew formulae
   depends_on 'orc' => :optional
@@ -50,8 +52,15 @@ class GstPluginsGood < Formula
       --with-default-videosink=ximagesink
       --disable-debug
       --disable-dependency-tracking
+      --disable-silent-rules
     ]
 
+    if build.with? "x11"
+      args << "--with-x"
+    else
+      args << "--without-x"
+    end
+
     if build.head?
       ENV.append "NOCONFIGURE", "yes"
       system "./autogen.sh"