libfreenct: support --universal

Closes Homebrew/homebrew#18962.

Formula/libfreenect.rb

@@ -7,10 +7,16 @@ class Libfreenect < Formula
 
   head 'https://github.com/OpenKinect/libfreenect.git'
 
+  option :universal
+
   depends_on 'cmake' => :build
   depends_on 'libusb'
 
   def install
+    if build.universal?
+      ENV.universal_binary
+      ENV['CMAKE_OSX_ARCHITECTURES'] = "i386;x86_64"
+    end
     mkdir "build" do
       system "cmake", "..", *std_cmake_args
       system "make install"