Fixed unused attributes problem

Author: Valery Kholodkov

ngx_http_upload_module.c

@@ -1851,7 +1851,7 @@ ngx_http_upload_merge_ranges(ngx_http_upload_ctx_t *u, ngx_http_upload_range_t *
     ngx_http_upload_merger_state_t ms;
     off_t        remaining;
     ssize_t      rc;
-    int          result;
+    __attribute__((__unused__)) int result;
     ngx_buf_t    in_buf;
     ngx_buf_t    out_buf;
     ngx_http_upload_loc_conf_t  *ulcf = ngx_http_get_module_loc_conf(u->request, ngx_http_upload_module);