Fix utf-8

backend/nix/stack-integration.nix

@@ -0,0 +1,16 @@
+let
+  sources = import ./sources.nix;
+  pkgs = import sources.nixpkgs { };
+in
+
+# See https://docs.haskellstack.org/en/stable/nix_integration/#using-a-custom-shellnix-file
+{ ghc }:
+
+pkgs.haskell.lib.buildStackProject {
+  inherit ghc;
+  name = "haskell-stack-nix";
+  # System dependencies needed at compilation time
+  buildInputs = [
+    pkgs.zlib
+  ];
+}