There are several test cases in the bpf directory are still using
exit 0 when they need to be skipped. Use kselftest framework skip
code instead so it can help us to distinguish the return status.

Criterion to filter out what should be fixed in bpf directory:
  grep -r "exit 0" -B1 | grep -i skip

This change might cause some false-positives if people are running
these test scripts directly and only checking their return codes,
which will change from 0 to 4. However I think the impact should be
small as most of our scripts here are already using this skip code.
And there will be no such issue if running them with the kselftest
framework.

Signed-off-by: Po-Hsu Lin <redacted>
---
 tools/testing/selftests/bpf/test_bpftool_build.sh | 5 ++++-
 tools/testing/selftests/bpf/test_xdp_meta.sh      | 5 ++++-
 tools/testing/selftests/bpf/test_xdp_vlan.sh      | 7 +++++--
 3 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/tools/testing/selftests/bpf/test_bpftool_build.sh b/tools/testing/selftests/bpf/test_bpftool_build.sh
index ac349a5..b6fab1e 100755
--- a/tools/testing/selftests/bpf/test_bpftool_build.sh
+++ b/tools/testing/selftests/bpf/test_bpftool_build.sh

@@ -1,6 +1,9 @@
 #!/bin/bash
 # SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
 
+# Kselftest framework requirement - SKIP code is 4.
+ksft_skip=4
+
 case $1 in
 	-h|--help)
 		echo -e "$0 [-j <n>]"

@@ -22,7 +25,7 @@ KDIR_ROOT_DIR=$(realpath $PWD/$SCRIPT_REL_DIR/../../../../)
 cd $KDIR_ROOT_DIR
 if [ ! -e tools/bpf/bpftool/Makefile ]; then
 	echo -e "skip:    bpftool files not found!\n"
-	exit 0
+	exit $ksft_skip
 fi
 
 ERROR=0

diff --git a/tools/testing/selftests/bpf/test_xdp_meta.sh b/tools/testing/selftests/bpf/test_xdp_meta.sh
index 637fcf4..fd3f218 100755
--- a/tools/testing/selftests/bpf/test_xdp_meta.sh
+++ b/tools/testing/selftests/bpf/test_xdp_meta.sh

@@ -1,5 +1,8 @@
 #!/bin/sh
 
+# Kselftest framework requirement - SKIP code is 4.
+ksft_skip=4
+
 cleanup()
 {
 	if [ "$?" = "0" ]; then