Add some comments regarding the static build options

flake.nix

@@ -26,13 +26,29 @@
           # And some build configuration.
           # See https://nixos.org/manual/nixpkgs/unstable/#haskell-packaging-helpers.
           [
-            # Remove warp which pulls GHC into the runtime deps for some reason.
+            # Configurable static build. Set cabal options...
+            compose.disableSharedExecutables
+            compose.disableSharedLibraries
+            # ... and link required static libraries.
+            (compose.appendConfigureFlags [
+              "--ghc-option=-optl=-static"
+              "--ghc-option=-optl=-pthread"
+              "--extra-lib-dirs=${pkgs.gmp6.override { withStatic = true; }}/lib"
+              "--extra-lib-dirs=${pkgs.zlib.static}/lib"
+              "--extra-lib-dirs=${pkgs.glibc.static}/lib"
+              "--extra-lib-dirs=${pkgs.libffi.overrideAttrs (old: { dontDisableStatic = true; })}/lib"
+            ])
+            # Remove all references to the Nix store from the executable.
+            # This is important because Nix uses the references for calculating
+            # what needs to be in the Docker container.
+            # FIXME: Using static linking, these references shouldn't even still be there.
+            # Can we somehow make GHC stop emitting them?
             (compose.overrideCabal (drv: {
               postInstall = ''
-                remove-references-to -t ${pkgs.haskellPackages.warp} $out/bin/utoy
+                ${pkgs.nukeReferences}/bin/nuke-refs $out/bin/utoy
               '';
             }))
-            # Return only the bin folder to curb image size
+            # Return only the bin folder to curb image size.
             compose.justStaticExecutables
           ];
       in {