anchor.diff:  , sslSupport ? false, openssl ? null
   , gnutlsSupport ? false, gnutls ? null
   , scpSupport ? false, libssh2 ? null
  -, gssSupport ? false, gss ? null
  +, gssSupport ? false, kerberos ? null
   , c-aresSupport ? false, c-ares ? null
   }:
   
  
positive.code:       ( if idnSupport then "--with-libidn=${libidn.dev}" else "--without-libidn" )
      ]
      ++ stdenv.lib.optional c-aresSupport "--enable-ares=${c-ares}"
      ++ stdenv.lib.optional gssSupport "--with-gssapi=${gss}";
  
    CXX = "c++";
    CXXCPP = "c++ -E";
  
negative.code:     optional idnSupport libidn ++
      optional ldapSupport openldap ++
      optional zlibSupport zlib ++
      optional gssSupport kerberos ++
      optional c-aresSupport c-ares ++
      optional sslSupport openssl ++
      optional gnutlsSupport gnutls ++
  