Move amazon option out of amazon-image.nix, needed to make ec2.hvm usable from nixops, without breaking evaluation for other backends.

(cherry picked from commit 213fe8427c5ce455b893c0c5c56cc38175bf36b7)

nixos/modules/module-list.nix

@@ -426,7 +426,7 @@
   ./virtualisation/docker.nix
   ./virtualisation/libvirtd.nix
   ./virtualisation/lxc.nix
-  #./virtualisation/nova.nix
+  ./virtualisation/amazon-options.nix
   ./virtualisation/openvswitch.nix
   ./virtualisation/parallels-guest.nix
   ./virtualisation/virtualbox-guest.nix

nixos/modules/virtualisation/amazon-image.nix

@@ -7,17 +7,6 @@ in
 {
   imports = [ ../profiles/headless.nix ./ec2-data.nix ];
 
-  options = {
-    ec2 = {
-      hvm = mkOption {
-        default = false;
-        description = ''
-          Whether the EC2 instance is a HVM instance.
-        '';
-      };
-    };
-  };
-
   config = {
     system.build.amazonImage =
       pkgs.vmTools.runInLinuxVM (

nixos/modules/virtualisation/amazon-options.nix

@@ -0,0 +1,16 @@
+{ config, lib, pkgs, ... }:
+{
+  options = {
+    ec2 = {
+      hvm = lib.mkOption {
+        default = false;
+        internal = true;
+        description = ''
+          Whether the EC2 instance is a HVM instance.
+        '';
+      };
+    };
+  };
+
+  config = {};
+}