net/tstun: use ts_omit_gro in another place I missed earlier

I didn't notice this GRO code during b3ae1cb0cc.

Updates #17283

Change-Id: I95c06c19e489097fc8d61180dc57ae4b8a69c58c
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

cmd/tailscaled/depaware-minbox.txt

@@ -68,7 +68,7 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
      💣 gvisor.dev/gvisor/pkg/sync                                   from gvisor.dev/gvisor/pkg/atomicbitops+
         gvisor.dev/gvisor/pkg/tcpip                                  from gvisor.dev/gvisor/pkg/tcpip/header+
      💣 gvisor.dev/gvisor/pkg/tcpip/checksum                         from gvisor.dev/gvisor/pkg/buffer+
-        gvisor.dev/gvisor/pkg/tcpip/header                           from tailscale.com/net/packet/checksum+
+        gvisor.dev/gvisor/pkg/tcpip/header                           from tailscale.com/net/packet/checksum
         gvisor.dev/gvisor/pkg/tcpip/seqnum                           from gvisor.dev/gvisor/pkg/tcpip/header
         gvisor.dev/gvisor/pkg/waiter                                 from gvisor.dev/gvisor/pkg/context+
         tailscale.com                                                from tailscale.com/version

net/tstun/wrap_linux.go

@@ -1,6 +1,8 @@
 // Copyright (c) Tailscale Inc & AUTHORS
 // SPDX-License-Identifier: BSD-3-Clause
 
+//go:build linux && !ts_omit_gro
+
 package tstun
 
 import (

net/tstun/wrap_noop.go

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