libc/eglibc: fix downloading of localedef addon

For the versions of eglibc where the ports addon is not external (ie,
all versions after, and including 2.17), we would fail to download the
localedef addon, since the test did not care about the addon we were
about to download, only whether the ports addon was external or not.

Fix that by skipping the ports addon only if that's the addon we're
trying to download.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>

 # This file adds functions to build the C library for bare metal (IE. none)

 # Copyright 2008 Yann E. MORIN

 # Licensed under the GPL v2. See COPYING in the root of this package

 do_libc_get() {

     :

 }

 do_libc_extract() {

     :

 }

 do_libc_check_config() {

     :

 }

 do_libc_start_files() {

     :

 }

 do_libc() {

     :

 }