cgal: use new dsl

Formula/cgal.rb

@@ -5,23 +5,21 @@ class Cgal < Formula
   url 'https://gforge.inria.fr/frs/download.php/31175/CGAL-4.0.2.tar.gz'
   sha1 'e80af4b1da25690df63ce83dd083710cc3db9697'
 
+  option 'imaging', "Build ImageIO and QT compoments of CGAL"
+
   depends_on 'cmake' => :build
   depends_on 'boost'
   depends_on 'gmp'
   depends_on 'mpfr'
 
-  depends_on 'qt' if ARGV.include? '--imaging'
-
-  def options
-    [['--imaging', "Build ImageIO and QT compoments of CGAL"]]
-  end
+  depends_on 'qt' if build.include? 'imaging'
 
   def install
     args = ["-DCMAKE_INSTALL_PREFIX=#{prefix}",
             "-DCMAKE_BUILD_TYPE=Release",
             "-DCMAKE_BUILD_WITH_INSTALL_RPATH=ON",
             "-DCMAKE_INSTALL_NAME_DIR=#{HOMEBREW_PREFIX}/lib"]
-    unless ARGV.include? '--imaging'
+    unless build.include? 'imaging'
       args << "-DWITH_CGAL_Qt3=OFF" << "-DWITH_CGAL_Qt4=OFF" << "-DWITH_CGAL_ImageIO=OFF"
     end
     args << '.'