anchor.diff:  , openssl ? null
   , cyrus_sasl ? null
   , gpgme ? null
  +, kerberos ? null
   , headerCache  ? true
   , sslSupport   ? true
   , saslSupport  ? true
   , gpgmeSupport ? true
   , imapSupport  ? true
   , withSidebar  ? true
  +, gssSupport   ? true
   }:
   
   assert headerCache  -> gdbm       != null;
  
positive.code:     # I set the value 'mailbox' because it is a default in the configure script
      "--with-homespool=mailbox"
    ] ++ optional sslSupport  "--with-ssl"
      ++ optional saslSupport "--with-sasl";
  
    meta = {
  
negative.code:     [ ncurses which perl ]
      ++ optional headerCache  gdbm
      ++ optional sslSupport   openssl
      ++ optional gssSupport   kerberos
      ++ optional saslSupport  cyrus_sasl
      ++ optional gpgmeSupport gpgme;
  
  