nix: use newer version of app2unit (#419)

flake.nix

@@ -35,6 +35,7 @@
           withX11 = false;
           withI3 = false;
         };
+        app2unit = pkgs.callPackage ./nix/app2unit.nix {inherit pkgs;};
         caelestia-cli = inputs.caelestia-cli.packages.${pkgs.system}.default;
       };
       with-cli = caelestia-shell.override {withCli = true;};

nix/app2unit.nix

@@ -0,0 +1,14 @@
+{
+  pkgs, # To ensure the nixpkgs version of app2unit
+  fetchFromGitHub,
+  ...
+}:
+pkgs.app2unit.overrideAttrs (final: prev: rec {
+  version = "1.0.3"; # Fix old issue related to missing env var
+  src = fetchFromGitHub {
+    owner = "Vladimir-csp";
+    repo = "app2unit";
+    tag = "v${version}";
+    hash = "sha256-7eEVjgs+8k+/NLteSBKgn4gPaPLHC+3Uzlmz6XB0930=";
+  };
+})