!733 修复dlopen失败dlerror返回值为null

Merge pull request !733 from maweiye/add-dlerror-info

porting/linux/user/ldso/dynlink.c

@@ -3074,6 +3074,10 @@ static void *dlopen_impl(
 			goto end;
 		}
 		if (!load_library_header(task)) {
+			error(noload ?
+				"Library %s is not already loaded" :
+				"Error loading shared library %s: %m",
+				file);
 			LD_LOGE("dlopen_impl load library header failed for %{public}s", task->name);
 			goto end;
 		}