use get-flake to build horizon-gen-nix

flake.lock

@@ -104,6 +104,21 @@
         "type": "github"
       }
     },
+    "get-flake": {
+      "locked": {
+        "lastModified": 1644686428,
+        "narHash": "sha256-zkhYsURWFrvEZLkIoBeqFBzSu+cA2u5mo6M8vq9LN7M=",
+        "owner": "ursi",
+        "repo": "get-flake",
+        "rev": "703f15558daa56dfae19d1858bb3046afe68831a",
+        "type": "github"
+      },
+      "original": {
+        "owner": "ursi",
+        "repo": "get-flake",
+        "type": "github"
+      }
+    },
     "horizon-gen-nix": {
       "inputs": {
         "cabal2nix": "cabal2nix",
@@ -289,6 +304,7 @@
     "root": {
       "inputs": {
         "flake-utils": "flake-utils",
+        "get-flake": "get-flake",
         "horizon-gen-nix": "horizon-gen-nix",
         "lint-utils": "lint-utils_3",
         "nixpkgs": "nixpkgs_5"

flake.nix

 {
   inputs = {
+    get-flake.url = "github:ursi/get-flake";
     lint-utils.url = "git+https://gitlab.homotopic.tech/nix/lint-utils";
-    horizon-gen-nix.url = "git+https://gitlab.homotopic.tech/horizon/horizon-gen-nix";
+    horizon-gen-nix = {
+      flake = false;
+      url = "git+https://gitlab.homotopic.tech/horizon/horizon-gen-nix";
+    };
     nixpkgs.url = "github:nixos/nixpkgs/nixpkgs-unstable";
   };
-  outputs = inputs@{ self, nixpkgs, flake-utils, horizon-gen-nix, lint-utils, ... }:
+  outputs = inputs@{ self, nixpkgs, flake-utils, get-flake, horizon-gen-nix, lint-utils, ... }:
     flake-utils.lib.eachSystem [ "x86_64-linux" ] (system:
       let
         pkgs = import nixpkgs { inherit system; };
+        horizon-gen-nix-app = get-flake horizon-gen-nix;
         overrides-hp = import ./overlay.nix { inherit inputs pkgs; };
         configuration = import ./configuration.nix { inherit inputs pkgs; };
         hp = pkgs.haskell.packages.ghc942.override {
@@ -26,7 +31,7 @@
         apps = {
           horizon-gen-nix = {
             type = "app";
-            program = "${horizon-gen-nix.outputs.packages.x86_64-linux.default}/bin/horizon-gen-nix";
+            program = "${horizon-gen-nix-app.outputs.packages.${system}.default}/bin/horizon-gen-nix";
           };
           horizon-gen-gitlab-ci = {
             type = "app";