use content addressing

flake.lock

@@ -272,6 +272,22 @@
         "type": "github"
       }
     },
+    "per-system-optim": {
+      "flake": false,
+      "locked": {
+        "lastModified": 1688657169,
+        "narHash": "sha256-eKvcoQ18D1drdn3afR+L3ZiRLRvaNnfqF3W+GZzf15s=",
+        "ref": "refs/heads/main",
+        "rev": "e20724603b6eb99d50a09fe2371b54b01dd4860d",
+        "revCount": 9,
+        "type": "git",
+        "url": "https://git.chir.rs/darkkirb/per-system-optim"
+      },
+      "original": {
+        "type": "git",
+        "url": "https://git.chir.rs/darkkirb/per-system-optim"
+      }
+    },
     "root": {
       "inputs": {
         "attic": "attic",
@@ -280,7 +296,8 @@
         "gomod2nix": "gomod2nix",
         "hydra": "hydra",
         "mautrix-cleanup": "mautrix-cleanup",
-        "nixpkgs": "nixpkgs_2"
+        "nixpkgs": "nixpkgs_2",
+        "per-system-optim": "per-system-optim"
       }
     },
     "rust-overlay": {

flake.nix

@@ -26,6 +26,10 @@
     hydra = {
       url = "git+https://git.chir.rs/darkkirb/hydra";
     };
+    per-system-optim = {
+      url = "git+https://git.chir.rs/darkkirb/per-system-optim";
+      flake = false;
+    };
   };
 
   outputs = {
@@ -33,14 +37,17 @@
     nixpkgs,
     flake-utils,
     hydra,
+    per-system-optim,
     ...
   }:
-    flake-utils.lib.eachSystem ["aarch64-darwin" "aarch64-linux" "x86_64-darwin" "x86_64-linux" "riscv64-linux"] (
+    flake-utils.lib.eachSystem ["aarch64-linux" "x86_64-linux" "riscv64-linux"] (
       system: let
-        pkgs = import nixpkgs {
+        nixpkgs-patched = (import "${per-system-optim}/nixpkgs/eval.nix" {inherit nixpkgs;}).${system};
+        pkgs = import nixpkgs-patched {
           inherit system;
           config.allowUnfree = true;
           config.allowUnsupportedSystem = true;
+          config.contentAddressedByDefault = true;
           overlays = [
             self.overlays.${system}.default
           ];

hydra/default.nix

@@ -3,13 +3,24 @@
   nixpkgs,
   system,
 }: let
-  pkgs = import nixpkgs {
+  pkgs' = import nixpkgs {
     inherit system;
     config = {
       allowUnfree = true;
       allowUnsupportedSystem = true;
     };
   };
+  lib = import ../lib {pkgs = pkgs';};
+  flake = (lib.importFlake {inherit system;}).defaultNix;
+  nixpkgs-patched = (import "${flake.inputs.per-system-optim}/nixpkgs/eval.nix" {inherit nixpkgs;}).${system};
+  pkgs = import nixpkgs-patched {
+    inherit system;
+    config = {
+      allowUnfree = true;
+      allowUnsupportedSystem = true;
+      contentAddressedByDefault = true;
+    };
+  };
   ci = import nix-packages {inherit pkgs;};
   isReserved = n: n == "lib" || n == "overlays" || n == "modules";
 in