selftests: dsa: Replace test symlinks by wrapper script

The dsa tests which are symlinks of tests from net/forwarding/ (like
tc_actions.sh) become regular files after export (because `rsync
--copy-unsafe-links` is used) and expect to source lib.sh
(net/forwarding/lib.sh) from the same directory.

In the last patch of this series, net/forwarding/lib.sh will source lib.sh
from its parent directory (ie. net/lib.sh). This would not work for dsa
tests because net/lib.sh is not present under drivers/net/.

Since the tests in net/forwarding/ are not meant to be copied and run from
another directory, as a preparation for that last patch, replace the test
symlinks by a wrapper script which runs the original tests under
net/forwarding/. Following from that, the links to shared library scripts
in dsa/ are no longer used so remove them and add all the original files
needed from parent directories to TEST_INCLUDES.

Suggested-by: Hangbin Liu <[e-mail]>
Reviewed-by: Petr Machata <[e-mail]>
Tested-by: Petr Machata <[e-mail]>
Reviewed-by: Hangbin Liu <[e-mail]>
Signed-off-by: Benjamin Poirier <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

tools/testing/selftests/drivers/net/dsa/Makefile

···
 	tc_actions.sh \
 	test_bridge_fdb_stress.sh
 
-TEST_PROGS_EXTENDED := lib.sh tc_common.sh
+TEST_FILES := \
+	run_net_forwarding_test.sh \
+	forwarding.config
 
-TEST_FILES := forwarding.config
+TEST_INCLUDES := \
+	../../../net/forwarding/bridge_locked_port.sh \
+	../../../net/forwarding/bridge_mdb.sh \
+	../../../net/forwarding/bridge_mld.sh \
+	../../../net/forwarding/bridge_vlan_aware.sh \
+	../../../net/forwarding/bridge_vlan_mcast.sh \
+	../../../net/forwarding/bridge_vlan_unaware.sh \
+	../../../net/forwarding/lib.sh \
+	../../../net/forwarding/local_termination.sh \
+	../../../net/forwarding/no_forwarding.sh \
+	../../../net/forwarding/tc_actions.sh \
+	../../../net/forwarding/tc_common.sh
 
 include ../../../lib.mk

tools/testing/selftests/drivers/net/dsa/run_net_forwarding_test.sh

···
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+
+libdir=$(dirname "$(readlink -f "${BASH_SOURCE[0]}")")
+testname=$(basename "${BASH_SOURCE[0]}")
+
+source "$libdir"/forwarding.config
+cd "$libdir"/../../../net/forwarding/ || exit 1
+source "./$testname" "$@"

tools/testing/selftests/drivers/net/dsa/test_bridge_fdb_stress.sh

···
 REQUIRE_MZ="no"
 NETIF_CREATE="no"
 lib_dir=$(dirname "$0")
-source "$lib_dir"/lib.sh
+source "$lib_dir"/../../../net/forwarding/lib.sh
 
 cleanup() {
 	echo "Cleaning up"