anchor.diff:      (enFlag "gl" (mesa != null) null)
       #(enFlag "gtk3" ( != null) null)
       #(enFlag "qt" ( != null) null)
  +    #"--disable-vulkan"
       (enFlag "libvisual" (libvisual != null) null)
       #(enFlag "timidity" ( != null) null)
       #(enFlag "teletextdec" ( != null) null)
  
positive.code:     "--disable-examples"
      "--enable-external"
      "--enable-experimental"
      "--enable-introspection"
      "--disable-gtk-doc"
      "--disable-gtk-doc-html"
      "--disable-gtk-doc-pdf"
      "--enable-gobject-cast-checks"
      "--enable-glib-asserts"
      (enFlag "orc" (orc != null) null)
      "--disable-static-plugins"
      # Internal Plugins
  
negative.code:     (enFlag "modplug" (libmodplug != null) null)
      #(enFlag "mimic" ( != null) null)
      #(enFlag "mpeg2enc" ( != null) null)
      #(enFlag "mplex" ( != null) null)
      (enFlag "musepack" (musepack != null) null)
      #(enFlag "nas" ( != null) null)
  