Clean up nix-store on the machines with limited disk space

morph/lib/issuer-aws.nix

@@ -17,4 +17,10 @@
   # morph-supplied name.  See also
   # <https://github.com/DBCDK/morph/issues/146>.
   networking.hostName = name;
+
+  # Clean up packages after a while
+  nix.gc = {
+    automatic = true;
+    dates = "weekly";
+  };
 }