Cache `Tty.width`, since it is used heavily because of `ohai`.

Library/Homebrew/utils/tty.rb

@@ -6,10 +6,12 @@ module Tty
   end
 
   def width
-    width = `/bin/stty size 2>/dev/null`.split[1]
-    width = `/usr/bin/tput cols 2>/dev/null`.split[0] if width.to_i.zero?
-    width ||= 80
-    width.to_i
+    @width ||= begin
+      width = `/bin/stty size 2>/dev/null`.split[1]
+      width = `/usr/bin/tput cols 2>/dev/null`.split[0] if width.to_i.zero?
+      width ||= 80
+      width.to_i
+    end
   end
 
   def truncate(string)