cmd/tailscaled, net/tstun: add build tags to omit BIRD and TAP

Signed-off-by: Andrew Dunham <andrew@du.nham.ca>
Change-Id: I7a39f4eeeb583b73ecffaf4c5f086a38e3a53e2e

net/tstun/tap_linux.go

@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build !ts_omit_tap
+
 package tstun
 
 import (