Add https://www.kernel.org/pub to the list of mirrors.

[krasin]

Recently, it was announced that kernel.org will shutdown their FTP
servers: https://kernel.org/shutting-down-ftp-services.html

In fact, the FTP server that hosts kernel sources went offline today.
That caused downloads to fail, and it has become impossible to build
the VoCore2 OpenWRT image.

This change adds the new HTTPS mirror that is here to stay.

[krasin]

Alternatively, we can cherry pick the following mainline commit: openwrt/openwrt@1f9e25d (only found it out after fixing the issue locally)

[krasin]

@noblepepper Friendly ping. At the time of writing, nobody can build the firmware image for VoCore2. See the exact output below.

To reproduce it locally, you might need to delete the cached linux kernel sources tarbal from dl/linux-3.18.45.tar.xz

make[1]: Entering directory '/home/user/src/github.com/noblepepper/openwrt-chaoscalmer/target/linux'
make[2]: Entering directory '/home/user/src/github.com/noblepepper/openwrt-chaoscalmer/target/linux/ramips'
mkdir -p /home/user/src/github.com/noblepepper/openwrt-chaoscalmer/dl
/home/user/src/github.com/noblepepper/openwrt-chaoscalmer/scripts/download.pl "/home/user/src/github.com/noblepepper/openwrt-chaoscalmer/dl" "linux-3.18.45.tar.xz" "c527bae0aa1a5d6f3ebe31ad348c5339" "" "@KERNEL/linux/kernel/v3.x"
--2017-03-02 15:18:31--  ftp://ftp.all.kernel.org/pub/linux/kernel/v3.x/linux-3.18.45.tar.xz
           => '-'
Resolving ftp.all.kernel.org (ftp.all.kernel.org)... failed: Name or service not known.
wget: unable to resolve host address 'ftp.all.kernel.org'
Download failed.
--2017-03-02 15:18:31--  http://ftp.all.kernel.org/pub/linux/kernel/v3.x/linux-3.18.45.tar.xz
Resolving ftp.all.kernel.org (ftp.all.kernel.org)... failed: Name or service not known.
wget: unable to resolve host address 'ftp.all.kernel.org'
Download failed.
--2017-03-02 15:18:31--  ftp://ftp.all.kernel.org/pub/linux/kernel/v3.x/longterm/v3.18.45/linux-3.18.45.tar.xz
           => '-'
Resolving ftp.all.kernel.org (ftp.all.kernel.org)... failed: Name or service not known.
wget: unable to resolve host address 'ftp.all.kernel.org'
Download failed.
--2017-03-02 15:18:31--  http://ftp.all.kernel.org/pub/linux/kernel/v3.x/longterm/v3.18.45/linux-3.18.45.tar.xz
Resolving ftp.all.kernel.org (ftp.all.kernel.org)... failed: Name or service not known.
wget: unable to resolve host address 'ftp.all.kernel.org'
Download failed.
--2017-03-02 15:18:31--  http://mirror2.openwrt.org/sources/linux-3.18.45.tar.xz
Resolving mirror2.openwrt.org (mirror2.openwrt.org)... 46.4.11.11
Connecting to mirror2.openwrt.org (mirror2.openwrt.org)|46.4.11.11|:80... connected.
HTTP request sent, awaiting response... 404 Not Found
2017-03-02 15:18:31 ERROR 404: Not Found.

Download failed.
--2017-03-02 15:18:31--  http://downloads.openwrt.org/sources/linux-3.18.45.tar.xz
Resolving downloads.openwrt.org (downloads.openwrt.org)... 78.24.191.177
Connecting to downloads.openwrt.org (downloads.openwrt.org)|78.24.191.177|:80... connected.
HTTP request sent, awaiting response... 404 Not Found
2017-03-02 15:18:32 ERROR 404: Not Found.

Download failed.
No more mirrors to try - giving up.
Makefile:26: recipe for target '/home/user/src/github.com/noblepepper/openwrt-chaoscalmer/dl/linux-3.18.45.tar.xz' failed
make[2]: *** [/home/user/src/github.com/noblepepper/openwrt-chaoscalmer/dl/linux-3.18.45.tar.xz] Error 2
make[2]: Leaving directory '/home/user/src/github.com/noblepepper/openwrt-chaoscalmer/target/linux/ramips'
Makefile:13: recipe for target 'menuconfig' failed
make[1]: *** [menuconfig] Error 2
make[1]: Leaving directory '/home/user/src/github.com/noblepepper/openwrt-chaoscalmer/target/linux'
/home/user/src/github.com/noblepepper/openwrt-chaoscalmer/include/toplevel.mk:134: recipe for target 'kernel_menuconfig' failed
make: *** [kernel_menuconfig] Error 2

[krasin]

Apparently, I am not the only one who was hit by that: http://forum.vocore.io/viewtopic.php?f=16&t=3562

[noblepepper]

Apologies for the delay, I've been preoccupied by geriatric dogs and visiting family lately...

I merged your solution, I'm sure this will cause a conflict when OpenWrt gets around to updating Chaos Calmer with the change in trunk but I'll deal with that when it happens, one of my superpowers is procrastination.

Thanks for your contribution!

[krasin]

@noblepepper Thank you for merging and for maintaining the fork!