libbpf: Fix error path in bpf_object__elf_init()

When it failed to get section names, it should call into
bpf_object__elf_finish() like others.

Fixes: 88a82120 ("libbpf: Factor out common ELF operations and improve logging")
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20210317145414.884817-1-namhyung@kernel.org

tools/lib/bpf/libbpf.c

@@ -1181,7 +1181,8 @@ static int bpf_object__elf_init(struct bpf_object *obj)
 	if (!elf_rawdata(elf_getscn(obj->efile.elf, obj->efile.shstrndx), NULL)) {
 		pr_warn("elf: failed to get section names strings from %s: %s\n",
 			obj->path, elf_errmsg(-1));
-		return -LIBBPF_ERRNO__FORMAT;
+		err = -LIBBPF_ERRNO__FORMAT;
+		goto errout;
 	}
 
 	/* Old LLVM set e_machine to EM_NONE */