feat: lock the `nix build` to using the repo rust version

flake.lock

@@ -32,6 +32,22 @@
         "type": "indirect"
       }
     },
+    "nixpkgs-mozilla": {
+      "flake": false,
+      "locked": {
+        "lastModified": 1744624473,
+        "narHash": "sha256-S6zT/w5SyAkJ//dYdjbrXgm+6Vkd/k7qqUl4WgZ6jjk=",
+        "owner": "mozilla",
+        "repo": "nixpkgs-mozilla",
+        "rev": "2292d4b35aa854e312ad2e95c4bb5c293656f21a",
+        "type": "github"
+      },
+      "original": {
+        "owner": "mozilla",
+        "repo": "nixpkgs-mozilla",
+        "type": "github"
+      }
+    },
     "nixpkgs_2": {
       "locked": {
         "lastModified": 1722995383,
@@ -51,6 +67,7 @@
       "inputs": {
         "naersk": "naersk",
         "nixpkgs": "nixpkgs_2",
+        "nixpkgs-mozilla": "nixpkgs-mozilla",
         "utils": "utils"
       }
     },

flake.nix

@@ -4,6 +4,10 @@
   inputs = {
     nixpkgs.url = "nixpkgs/nixos-unstable";
     naersk.url = "github:nix-community/naersk";
+    nixpkgs-mozilla = {
+      url = "github:mozilla/nixpkgs-mozilla";
+      flake = false;
+    };
     utils.url = "github:numtide/flake-utils";
   };
 
@@ -17,12 +21,27 @@
     nixpkgs,
     utils,
     naersk,
+    nixpkgs-mozilla,
   }:
     utils.lib.eachDefaultSystem (
       system: let
         overrides = (builtins.fromTOML (builtins.readFile ./rust-toolchain.toml));
-        pkgs = (import nixpkgs) {inherit system;};
-        naersk' = pkgs.callPackage naersk {};
+        pkgs = (import nixpkgs) {
+          inherit system;
+
+          overlays = [
+            (import nixpkgs-mozilla)
+          ];
+        };
+        toolchain = (pkgs.rustChannelOf {
+          rustToolchain = ./rust-toolchain.toml;
+          sha256 = "sha256-KUm16pHj+cRedf8vxs/Hd2YWxpOrWZ7UOrwhILdSJBU=";
+        }).rust;
+
+        naersk' = pkgs.callPackage naersk {
+          cargo = toolchain;
+          rustc = toolchain;
+        };
         package_name = "skynet_discord_bot";
         desc = "Skynet Discord Bot";
         buildInputs = with pkgs; [