anchor.diff:  , zlibSupport ? true, zlib ? null
   , sslSupport ? zlibSupport, openssl ? null
   , gnutlsSupport ? false, gnutls ? null
  +, wolfsslSupport ? false, wolfssl ? null
   , scpSupport ? zlibSupport && !stdenv.isSunOS && !stdenv.isCygwin, libssh2 ? null
   , gssSupport ? !stdenv.hostPlatform.isWindows, libkrb5 ? null
   , c-aresSupport ? false, c-ares ? null
  
positive.code: assert zlibSupport -> zlib != null;
  assert sslSupport -> openssl != null;
  assert !(gnutlsSupport && sslSupport);
  assert gnutlsSupport -> gnutls != null;
  assert scpSupport -> libssh2 != null;
  assert c-aresSupport -> c-ares != null;
  assert brotliSupport -> brotli != null;
  
negative.code:       # to nss-cacert from the default profile.
        "--without-ca-bundle"
        "--without-ca-path"
        # The build fails when using wolfssl with --with-ca-fallback
        ( if wolfsslSupport then "--without-ca-fallback" else "--with-ca-fallback")
        "--disable-manual"
        ( if sslSupport then "--with-ssl=${openssl.dev}" else "--without-ssl" )
        ( if gnutlsSupport then "--with-gnutls=${gnutls.dev}" else "--without-gnutls" )
  