arch: allow adding a suffix to the arch-part of a tuple

For some architectures, it is legit to have an alternate value in the
'architecture' part of the tuple. For example:
armv5te-*
armv7a8-*

Besides, some packages expect the tuple to reflect the arch variant
(eg. openMPI) to detect the variant's capabilities (eg. atomic
primitives).

This patch adds an option for the user to specify a suffix to be added
to the arch-part of the tuple.

Signed-off-by: Willy Tarreau <w@1wt.eu>
Message-ID: <20130120225822.GS6838@1wt.eu>
Patch-Id: 213994
[yann.morin.1998@free.fr: make it a suffix, not an override]
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() {

     :

 }