fix(nix): use Flake for Nix sanity check

Author: lionello

Makefile

@@ -29,4 +29,5 @@ pkgs/npm/README.md src/README.md: README.md
 
 .PHONY: test-nix
 test-nix:
-	nix-shell --pure -E 'with import <nixpkgs> {}; mkShell { buildInputs = [ (import ./default.nix {}) ]; }' --run defang
+	nix run .#defang-cli
+

pkgs/defang/cli.nix

@@ -1,12 +1,12 @@
 {
-  buildGoModule,
+  buildGo124Module,
   installShellFiles,
   lib,
 }:
-buildGoModule {
+buildGo124Module {
   pname = "defang-cli";
   version = "git";
-  src = ../../src;
+  src = lib.cleanSource ../../src;
   vendorHash = "sha256-m8xBhpKS6Tvoik2WZbkWgM52/FkCEhbdFNRwByi30zw="; # TODO: use fetchFromGitHub
 
   subPackages = [ "cmd/cli" ];
@@ -33,5 +33,6 @@ buildGoModule {
     homepage = "https://defang.io/";
     license = licenses.mit;
     maintainers = with maintainers; [ lionello ];
+    mainProgram = "defang";
   };
 }