drizzle - don't strip bin/sbin

For whatever reason, stripping sbin/drizzled removes the symbol
_drizzled_auth_all_plugin_ which makes drizzled crash on start.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>

Formula/drizzle.rb

@@ -13,6 +13,8 @@ class Drizzle < Formula
   depends_on 'libgcrypt'
   depends_on 'readline'
 
+  skip_clean ['sbin', 'bin']
+
   def install
     system "./configure", "--disable-debug", "--disable-dependency-tracking",
                           "--prefix=#{prefix}"