anchor.diff:  assert gnutlsSupport -> gnutls != null;
   assert scpSupport -> libssh2 != null;
   assert c-aresSupport -> c-ares != null;
  +assert gssSupport -> kerberos != null;
   
   stdenv.mkDerivation rec {
     name = "curl-7.56.0";
  
positive.code: , sslSupport ? false, openssl ? null
  , gnutlsSupport ? false, gnutls ? null
  , scpSupport ? false, libssh2 ? null
  , gssSupport ? false, gss ? null
  , c-aresSupport ? false, c-ares ? null
  }:
  
  
negative.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=${kerberos}";
  
    CXX = "c++";
    CXXCPP = "c++ -E";
  