Fix mailserver DNS; Add local build machine; Add test Hydra jobs

system/dns.nix

@@ -10,6 +10,12 @@
       		    }
       		  }
 
+            mail.matri.cx {
+      		    template IN A  {
+      		        answer "{{ .Name }} 0 IN A 149.28.112.101"
+      		    }
+      		  }
+
       		  *.matri.cx {
       		    template IN A  {
       		        answer "{{ .Name }} 0 IN A 192.168.0.130"

system/nix-conf.nix

@@ -1,6 +1,13 @@
 { ... }: {
   nix = {
-    buildMachines = [ ];
+    buildMachines = [
+      {
+        hostName = "localhost";
+        system = "x86_64-linux";
+        supportedFeatures = [ "kvm" "nixos-test" "big-parallel" "benchmark" ];
+        maxJobs = 8;
+      }
+    ];
     distributedBuilds = false;
     settings = {
       auto-optimise-store = false; # https://github.com/NixOS/nix/issues/7273