nero: backport older linux-firmware to work around GCN video decode issues

flake.nix

@@ -2,6 +2,7 @@
   inputs = {
     nixpkgs.url = "github:NixOS/nixpkgs/nixos-26.05";
     nixpkgs-unstable.url = "github:NixOS/nixpkgs/nixos-unstable";
+    nixpkgs-firmware.url = "github:NixOS/nixpkgs?rev=220e781eee89fa86f26d05c40a57eea1c691adec";
 
     home-manager = {
       url = "github:nix-community/home-manager/release-26.05";
@@ -39,6 +40,7 @@
       self,
       nixpkgs,
       nixpkgs-xr,
+      nixpkgs-firmware,
       home-manager,
       nix-darwin,
       nix-flatpak,
@@ -58,6 +60,9 @@
           users.frank = ./home/frank.nix;
         };
       };
+
+      nixos-system = "x86_64-linux";
+      nixos-pkgs = nixpkgs.legacyPackages.${nixos-system};
     in
     {
       nixosConfigurations = {
@@ -74,6 +79,15 @@
 
             ./hosts/nero/hardware.nix
             ./hosts/nero/configuration.nix
+
+            {
+              nixpkgs.overlays = [
+                (final: prev: {
+                  linux-firmware =
+                    nixpkgs-firmware.legacyPackages.${nixos-pkgs.stdenv.hostPlatform.system}.linux-firmware;
+                })
+              ];
+            }
           ];
         };