tools/bpftool: Fix error return code in do_batch()

Fix to return a negative error code from the error handling
case instead of 0, as done elsewhere in this function.

Fixes: 668da745 ("tools: bpftool: add support for quotations ...")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Zhihao Cheng <chengzhihao1@huawei.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Reviewed-by: Quentin Monnet <quentin@isovalent.com>
Link: https://lore.kernel.org/bpf/20210609115916.2186872-1-chengzhihao1@huawei.com

tools/bpf/bpftool/main.c

@@ -341,8 +341,10 @@ static int do_batch(int argc, char **argv)
 		n_argc = make_args(buf, n_argv, BATCH_ARG_NB_MAX, lines);
 		if (!n_argc)
 			continue;
-		if (n_argc < 0)
+		if (n_argc < 0) {
+			err = n_argc;
 			goto err_close;
+		}
 
 		if (json_output) {
 			jsonw_start_object(json_wtr);