Set up Haven as a distributed build target for aarch64

hosts/Haven/default.nix

@@ -59,12 +59,17 @@ in
     };
   };
 
-  # Enable mdadm and Sapana (RAID 5 primary storage)
-  boot.swraid = {
+  boot = {
+    # Enable mdadm for Sapana (RAID 5 primary storage)
+    swraid = {
       enable = true;
       # mdadmConf configured in nix-secrets
     };
 
+    # Allow Haven to be a build target for other architectures (mainly ARM64)
+    binfmt.emulatedSystems = [ "aarch64-linux" ];
+  };
+
   # Open port for OpenVPN
   networking.firewall.allowedUDPPorts = [ 1194 ];