feat: support non-flake users

This uses flakes-compat to read the `flake.nix` and expose it
to non-flake users.

Signed-off-by: Raito Bezarius <masterancpp@gmail.com>

default.nix

@@ -0,0 +1,10 @@
+(import
+  (
+    let lock = builtins.fromJSON (builtins.readFile ./flake.lock); in
+    fetchTarball {
+      url = lock.nodes.flake-compat.locked.url or "https://github.com/edolstra/flake-compat/archive/${lock.nodes.flake-compat.locked.rev}.tar.gz";
+      sha256 = lock.nodes.flake-compat.locked.narHash;
+    }
+  )
+  { src = ./.; }
+).defaultNix

flake.lock

@@ -102,6 +102,22 @@
         "type": "github"
       }
     },
+    "flake-compat_2": {
+      "flake": false,
+      "locked": {
+        "lastModified": 1696426674,
+        "narHash": "sha256-kvjfFW7WAETZlt09AgDn1MrtKzP7t90Vf7vypd3OL1U=",
+        "owner": "edolstra",
+        "repo": "flake-compat",
+        "rev": "0f9255e01c2351cc7d116c072cb317785dd33b33",
+        "type": "github"
+      },
+      "original": {
+        "owner": "edolstra",
+        "repo": "flake-compat",
+        "type": "github"
+      }
+    },
     "flake-utils": {
       "locked": {
         "lastModified": 1667395993,
@@ -203,6 +219,7 @@
         "attic": "attic",
         "crane": "crane_2",
         "fenix": "fenix",
+        "flake-compat": "flake-compat_2",
         "flake-utils": "flake-utils_2",
         "nix-filter": "nix-filter",
         "nixpkgs": "nixpkgs_2"

flake.nix

@@ -3,6 +3,10 @@
     nixpkgs.url = "github:NixOS/nixpkgs?ref=nixos-unstable";
     flake-utils.url = "github:numtide/flake-utils";
     nix-filter.url = "github:numtide/nix-filter";
+    flake-compat = {
+      url = "github:edolstra/flake-compat";
+      flake = false;
+    };
 
     fenix = {
       url = "github:nix-community/fenix";