Update

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

@@ -1,4 +1,4 @@
-// Copyright (c) Tailscale Inc & AUTHORS
+// Copyright (c) Tailscale Inc & contributors
 // SPDX-License-Identifier: BSD-3-Clause
 
 // Package cibuild reports runtime CI information.
@@ -12,3 +12,15 @@ func On() bool {
 	// https://docs.github.com/en/actions/learn-github-actions/environment-variables#default-environment-variables
 	return os.Getenv("GITHUB_ACTIONS") != "" || os.Getenv("CI") == "true"
 }
+
+// OnTailscaleCI reports whether the current binary is executing on
+// tailscale/tailscale's own GitHub Actions CI, as opposed to a fork's CI
+// or an unrelated downstream CI (such as a Linux distribution's package
+// build infrastructure) that also sets the generic CI=true environment
+// variable.
+func OnTailscaleCI() bool {
+	// GITHUB_REPOSITORY_OWNER is set by GitHub Actions to the owner of
+	// the repository whose workflow is running. For pull requests, this
+	// is the base repository's owner, not the fork's.
+	return os.Getenv("GITHUB_REPOSITORY_OWNER") == "tailscale"
+}