WIP: flake: home-manager: export NixOS homes

WIP: this does not take into account the `profiles` which *also* setup
home-manager modules...

And here is what the last few commits were building up to.

This is neat, but won't be useful *very* often.

flake/home-manager.nix

@@ -40,6 +40,8 @@ let
   };
 
   mkHome = name: mkHomeCommon "${self}/hosts/homes/${name}";
+
+  mkNixosHome = name: mkHomeCommon "${self}/hosts/nixos/${name}/home.nix";
 in
 {
   hosts.homes = {
@@ -57,8 +59,17 @@ in
             # Default configuration
             ambroisie = system;
           };
+          homeManagerHomes = lib.mapAttrs mkHome allHomes;
+
+          filteredNixosHosts = lib.filterAttrs (_: v: v == system) hosts.nixos;
+          nixosHomes' = lib.mapAttrs mkNixosHome filteredNixosHosts;
+          nixosHomes = lib.mapAttrs' (host: lib.nameValuePair "ambroisie@${host}") nixosHomes';
         in
-        lib.mapAttrs mkHome allHomes;
+        lib.foldl' lib.mergeAttrs { }
+          [
+            homeManagerHomes
+            nixosHomes
+          ];
     };
   };
 }