net/routetable: don't try to fetch the route table on android

Android >=14 forbids the use of netlink sockets, and in some configurations
can kill apps that try.

Fixes #9836

Signed-off-by: David Anderson <dave@tailscale.com>

net/routetable/routetable_linux.go

@@ -1,7 +1,7 @@
 // Copyright (c) Tailscale Inc & AUTHORS
 // SPDX-License-Identifier: BSD-3-Clause
 
-//go:build linux
+//go:build linux && !android
 
 package routetable
 

net/routetable/routetable_other.go

@@ -1,7 +1,7 @@
 // Copyright (c) Tailscale Inc & AUTHORS
 // SPDX-License-Identifier: BSD-3-Clause
 
-//go:build !linux && !darwin && !freebsd
+//go:build android || (!linux && !darwin && !freebsd)
 
 package routetable