libbpf: Add btf__new_split() API that was declared but not implemented

Seems like original commit adding split BTF support intended to add
btf__new_split() API, and even declared it in libbpf.map, but never
added (trivial) implementation. Fix this.

Fixes: ba451366 ("libbpf: Implement basic split BTF support")
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/bpf/20240201172027.604869-4-andrii@kernel.org

tools/lib/bpf/btf.c

@@ -1079,6 +1079,11 @@ struct btf *btf__new(const void *data, __u32 size)
 	return libbpf_ptr(btf_new(data, size, NULL));
 }
 
+struct btf *btf__new_split(const void *data, __u32 size, struct btf *base_btf)
+{
+	return libbpf_ptr(btf_new(data, size, base_btf));
+}
+
 static struct btf *btf_parse_elf(const char *path, struct btf *base_btf,
 				 struct btf_ext **btf_ext)
 {

tools/lib/bpf/libbpf.map

@@ -245,7 +245,6 @@ LIBBPF_0.3.0 {
 		btf__parse_raw_split;
 		btf__parse_split;
 		btf__new_empty_split;
-		btf__new_split;
 		ring_buffer__epoll_fd;
 } LIBBPF_0.2.0;
 
@@ -411,5 +410,7 @@ LIBBPF_1.3.0 {
 } LIBBPF_1.2.0;
 
 LIBBPF_1.4.0 {
+	global:
 		bpf_token_create;
+		btf__new_split;
 } LIBBPF_1.3.0;