perf header: Don't write empty BPF/BTF info

JIRA: https://issues.redhat.com/browse/RHEL-78200

upstream
========
commit f0d0f97
Author: Ian Rogers <irogers@google.com>
Date: Fri Jun 6 23:12:38 2025 -0700

description
===========
If there are no values in bpf_prog_info or bpf_btf feature don't write
the data into the header.

    Signed-off-by: Ian Rogers <irogers@google.com>
    Link: https://lore.kernel.org/r/20250617223356.2752099-4-irogers@google.com
    Signed-off-by: Namhyung Kim <namhyung@kernel.org>

Signed-off-by: Anubhav Shelat <ashelat@redhat.com>

Author: AnubhavS1

tools/perf/util/header.c

@@ -1016,10 +1016,13 @@ static int write_bpf_prog_info(struct feat_fd *ff,
 	struct perf_env *env = &ff->ph->env;
 	struct rb_root *root;
 	struct rb_node *next;
-	int ret;
+	int ret = 0;
 
 	down_read(&env->bpf_progs.lock);
 
+	if (env->bpf_progs.infos_cnt == 0)
+		goto out;
+
 	ret = do_write(ff, &env->bpf_progs.infos_cnt,
 		       sizeof(env->bpf_progs.infos_cnt));
 	if (ret < 0)
@@ -1058,10 +1061,13 @@ static int write_bpf_btf(struct feat_fd *ff,
 	struct perf_env *env = &ff->ph->env;
 	struct rb_root *root;
 	struct rb_node *next;
-	int ret;
+	int ret = 0;
 
 	down_read(&env->bpf_progs.lock);
 
+	if (env->bpf_progs.btfs_cnt == 0)
+		goto out;
+
 	ret = do_write(ff, &env->bpf_progs.btfs_cnt,
 		       sizeof(env->bpf_progs.btfs_cnt));