anchor.diff:  { stdenv
   , fetchurl, perl, gcc
  -, ncurses5, gmp, glibc, libiconv
  +, ncurses5, ncurses6, gmp, glibc, libiconv
   , llvmPackages
   }:
   
  
positive.code:     '' +
      # Rename needed libraries and binaries, fix interpreter
      stdenv.lib.optionalString stdenv.isLinux ''
        find . -type f -perm -0100 -exec patchelf \
            --replace-needed libncurses${stdenv.lib.optionalString stdenv.is64bit "w"}.so.5 libncurses.so \
            --replace-needed libtinfo.so libtinfo.so.5 \
            --interpreter ${glibcDynLinker} {} \;
  
        sed -i "s|/usr/bin/perl|perl\x00        |" ghc-${version}/ghc/stage2/build/tmp/ghc-stage2
  
negative.code:   # https://downloads.haskell.org/~ghc/8.6.5/
    src = fetchurl ({
      i686-linux = {
        # Don't use the Fedora27 build (as below) because there isn't one!
        url = "http://haskell.org/ghc/dist/${version}/ghc-${version}-i386-deb9-linux.tar.xz";
        sha256 = "1p2h29qghql19ajk755xa0yxkn85slbds8m9n5196ris743vkp8w";
      };
      x86_64-linux = {
        # This is the Fedora build because it links against ncurses6 where the
        # deb9 one links against ncurses5, see here
        # https://github.com/NixOS/nixpkgs/issues/85924 for a discussion
        url = "http://haskell.org/ghc/dist/${version}/ghc-${version}-x86_64-fedora27-linux.tar.xz";
        sha256 = "18dlqm5d028fqh6ghzn7pgjspr5smw030jjzl3kq6q1kmwzbay6g";
      };
      aarch64-linux = {
        url = "http://haskell.org/ghc/dist/${version}/ghc-${version}-aarch64-ubuntu18.04-linux.tar.xz";
  