Add elara sas specialisation

Signed-off-by: Nikolaos Karaolidis <nick@karaolidis.com>

hosts/common/configs/system/nixpkgs/default.nix

@@ -1,6 +1,9 @@
-{ inputs, ... }:
+{ inputs, system, ... }:
 {
   imports = [ inputs.nur.modules.nixos.default ];
 
-  nixpkgs.config.allowUnfree = true;
+  nixpkgs = {
+    hostPlatform = system;
+    config.allowUnfree = true;
+  };
 }