anchor.diff:  { config, stdenv, lib, fetchurl, fetchpatch
   , perl, pkg-config
   , libcap, libtool, libxml2, openssl, libuv, nghttp2, jemalloc
  +, enablePython ? false, python3
   , enableGSSAPI ? true, libkrb5
  -, enablePython ? false, python3
  -, enableSeccomp ? false, libseccomp
   , buildPackages, nixosTests
   }:
   
  
positive.code:   nativeBuildInputs = [ perl pkg-config ];
    buildInputs = [ libtool libxml2 openssl libuv nghttp2 jemalloc ]
      ++ lib.optional stdenv.isLinux libcap
      ++ lib.optional enableSeccomp libseccomp
      ++ lib.optional enableGSSAPI libkrb5
      ++ lib.optional enablePython (python3.withPackages (ps: with ps; [ ply ]));
  
  
negative.code: 
    configureFlags = [
      "--localstatedir=/var"
      "--without-lmdb"
    ] ++ lib.optional enableGSSAPI "--with-gssapi=${libkrb5.dev}/bin/krb5-config"
      ++ lib.optional (stdenv.hostPlatform != stdenv.buildPlatform) "BUILD_CC=$(CC_FOR_BUILD)";
  
    postInstall = ''
  