all: add ts_omit_tailnetlock as a start of making it build-time modular

Updates #17115

Change-Id: I6b083c0db4c4d359e49eb129d626b7f128f0a9d2
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

ipn/ipnlocal/tailnetlock_disabled.go

@@ -0,0 +1,31 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+//go:build ts_omit_tailnetlock
+
+package ipnlocal
+
+import (
+	"tailscale.com/ipn"
+	"tailscale.com/ipn/ipnstate"
+	"tailscale.com/tka"
+	"tailscale.com/types/netmap"
+)
+
+type tkaState struct {
+	authority *tka.Authority
+}
+
+func (b *LocalBackend) initTKALocked() error {
+	return nil
+}
+
+func (b *LocalBackend) tkaSyncIfNeeded(nm *netmap.NetworkMap, prefs ipn.PrefsView) error {
+	return nil
+}
+
+func (b *LocalBackend) tkaFilterNetmapLocked(nm *netmap.NetworkMap) {}
+
+func (b *LocalBackend) NetworkLockStatus() *ipnstate.NetworkLockStatus {
+	return &ipnstate.NetworkLockStatus{Enabled: false}
+}