Fix exiting the debugger menu with CTRL-D

Library/Homebrew/debrew.rb

@@ -62,7 +62,8 @@ module Debrew
         menu.entries.each_with_index { |e, i| puts "#{i+1}. #{e.name}" }
         print menu.prompt unless menu.prompt.nil?
 
-        input = $stdin.gets.chomp
+        input = $stdin.gets or exit
+        input.chomp!
 
         i = input.to_i
         if i > 0
@@ -103,6 +104,8 @@ module Debrew
 
     begin
       yield
+    rescue SystemExit
+      original_raise
     rescue Exception => e
       debug(e)
     ensure