[FS#731] Offline build not possible after "make download"

[LEDE Bugs]

A new Flyspray task has been opened.  Details are below. 

User who did this - Daniel Haid (D.H.) 

Attached to Project - LEDE Project
Summary - Offline build not possible after "make download"
Task Type - Bug Report
Category - Base system
Status - Unconfirmed
Assigned To - 
Operating System - All
Severity - Medium
Priority - Very Low
Reported Version - lede-17.01
Due in Version - Undecided
Due Date - Undecided
Details - I tried to do an offline build of almost the default configuration for x86_64 of 17.01.1. So I did "make download" (with that configuration) on a machine connected to the internet and then tried to build from there offline, but "make" tried to download files, that "make download" did not and failed.

The first few files were the following, then I gave up:

ncurses-6.0.tar.gz
lzo-2.09.tar.gz
usign-2015-07-04-ef641914.tar.xz
mbedtls-2.4.2-gpl.tgz
ustream-ssl-2016-07-02-ec80adaa.tar.xz
openssl-1.0.2k.tar.gz

More information can be found at the following URL:
https://bugs.lede-project.org/index.php?do=details&task_id=731