Merge: rtla: Define _GNU_SOURCE in timerlat_bpf.c

MR: https://gitlab.com/redhat/centos-stream/src/kernel/centos-stream-10/-/merge_requests/982

# Merge Request Required Information

JIRA: https://issues.redhat.com/browse/RHEL-94187

## Summary of Changes

Fix missed definition which broke rtla when glibc was updated in RHEL. Note: the update is not in CentOS Stream 10 yet, but this is needed nevertheless.

## Approved Development Ticket(s)
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Please follow the CentOS Stream [contribution documentation](https://docs.centos.org/en-US/stream-contrib/quickstart/) for how to file this ticket and have it approved.

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Signed-off-by: Tomas Glozar <tglozar@redhat.com>

Approved-by: Luis Claudio R. Goncalves <lgoncalv@redhat.com>
Approved-by: Wander Lairson Costa <wander@redhat.com>
Approved-by: Juri Lelli <juri.lelli@redhat.com>
Approved-by: CKI KWF Bot <cki-ci-bot+kwf-gitlab-com@redhat.com>

Merged-by: CKI GitLab Kmaint Pipeline Bot <26919896-cki-kmaint-pipeline-bot@users.noreply.gitlab.com>

Author: CKI KWF Bot

tools/tracing/rtla/src/timerlat_bpf.c

@@ -1,5 +1,6 @@
 // SPDX-License-Identifier: GPL-2.0
 #ifdef HAVE_BPF_SKEL
+#define _GNU_SOURCE
 #include "timerlat.h"
 #include "timerlat_bpf.h"
 #include "timerlat.skel.h"