btf__add_type_tag
LIBBPF_API int btf__add_type_tag(struct btf *btf, const char *value, int ref_type_id);
id = btf__add_type_tag(btf, "void_tag", 0);
btf__add_type_tag(btf, "typetag", 6); /* [19] typetag union u1; */
id = btf__add_type_tag(btf, "tag1", 1);