use bdwgc from sydpkgs

flake.nix

@@ -3,9 +3,13 @@
     haskellNix.url = "github:input-output-hk/haskell.nix";
     # nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
     nixpkgs.follows = "haskellNix/nixpkgs-unstable";
+    sydpkgs = {
+      url = "git+https://git.deertopia.net/msyds/sydpkgs";
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
   };
 
-  outputs = { self, nixpkgs, haskellNix, ... }@inputs:
+  outputs = { self, nixpkgs, sydpkgs, haskellNix, ... }@inputs:
     let
       supportedSystems = [
         "aarch64-darwin" "aarch64-linux"
@@ -15,21 +19,10 @@
       overlays = [
         haskellNix.overlay
         (final: prev: {
-          bdwgc = final.callPackage ./bdwgc.nix {};
+          inherit (sydpkgs.packages.${final.stdenv.hostPlatform.system})
+            bdwgc;
         })
         (final: prev: {
-          # haskellPackages = prev.haskellPackages.override {
-          #   qbe = final.haskell-nix.project' {
-          #     src = final.fetchFromGitea {
-          #       domain = "git.deertopia.net";
-          #       owner = "msyds";
-          #       repo = "qbe-hs";
-          #       rev = "master";
-          #       hash = "sha256-3Ni2xFOvw7Qjzq7BIXfnSQQ3U99OaEH0j6SdILMYizs=";
-          #     };
-          #     compiler-nix-name = "ghc912";
-          #   };
-          # };
           gyehoek = final.haskell-nix.project' {
             src = ./.;
             compiler-nix-name = "ghc912";