Update dependencies

vendor/tailscale.com/util/cibuild/cibuild.go

@@ -0,0 +1,14 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Package cibuild reports runtime CI information.
+package cibuild
+
+import "os"
+
+// On reports whether the current binary is executing on a CI system.
+func On() bool {
+	// CI env variable is set by GitHub.
+	// https://docs.github.com/en/actions/learn-github-actions/environment-variables#default-environment-variables
+	return os.Getenv("GITHUB_ACTIONS") != "" || os.Getenv("CI") == "true"
+}