Use hut nix cache in owl1, owl2 and raccoon

For owl1 and owl2 directly connect to hut via LAN with HTTP, but for
raccoon pass via the proxy using jungle.bsc.es with HTTPS. There is no
risk of tampering as packages are signed.

m/common/xeon/net.nix

@@ -11,7 +11,7 @@
 
     proxy = {
       default = "http://hut:23080/";
-      noProxy = "127.0.0.1,localhost,internal.domain,10.0.40.40";
+      noProxy = "127.0.0.1,localhost,internal.domain,10.0.40.40,hut";
       # Don't set all_proxy as go complains and breaks the gitlab runner, see:
       # https://github.com/golang/go/issues/16715
       allProxy = null;

m/module/hut-substituter.nix

@@ -0,0 +1,10 @@
+{ config, ... }:
+{
+  nix.settings =
+    # Don't add hut as a cache to itself
+    assert config.networking.hostName != "hut";
+    {
+      substituters = [ "http://hut/cache" ];
+      trusted-public-keys = [ "jungle.bsc.es:pEc7MlAT0HEwLQYPtpkPLwRsGf80ZI26aj29zMw/HH0=" ];
+    };
+}

m/owl1/configuration.nix

@@ -8,6 +8,7 @@
     ../module/slurm-client.nix
     ../module/slurm-firewall.nix
     ../module/debuginfod.nix
+    ../module/hut-substituter.nix
   ];
 
   # Select the this using the ID to avoid mismatches

m/owl2/configuration.nix

@@ -8,6 +8,7 @@
     ../module/slurm-client.nix
     ../module/slurm-firewall.nix
     ../module/debuginfod.nix
+    ../module/hut-substituter.nix
   ];
 
   # Select the this using the ID to avoid mismatches

m/raccoon/configuration.nix

@@ -25,6 +25,11 @@
     } ];
   };
 
+  nix.settings = {
+    substituters = [ "https://jungle.bsc.es/cache" ];
+    trusted-public-keys = [ "jungle.bsc.es:pEc7MlAT0HEwLQYPtpkPLwRsGf80ZI26aj29zMw/HH0=" ];
+  };
+
   # Configure Nvidia driver to use with CUDA
   hardware.nvidia.package = config.boot.kernelPackages.nvidiaPackages.production;
   hardware.graphics.enable = true;