project: add dagger.lock to gitignore when pulling an external dep

Signed-off-by: Sam Alba <samalba@users.noreply.github.com>

state/project.go

@@ -387,10 +387,10 @@ func vendorUniverse(ctx context.Context, p string) error {
 		return err
 	}
 
-	// add universe to `.gitignore`
+	// add universe and lock file to `.gitignore`
 	if err := os.WriteFile(
 		path.Join(p, "cue.mod", "pkg", ".gitignore"),
-		[]byte(fmt.Sprintf("# dagger universe\n%s\n", stdlib.PackageName)),
+		[]byte(fmt.Sprintf("# generated by dagger\n%s\ndagger.lock\n", stdlib.PackageName)),
 		0600,
 	); err != nil {
 		return err