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>

CT_EXPERIMENTAL=y

CT_LOCAL_TARBALLS_DIR="${HOME}/src"

CT_SAVE_TARBALLS=y

CT_LOG_EXTRA=y

CT_ARCH_mips=y

CT_TARGET_VENDOR="malta"

CT_KERNEL_linux=y

CT_KERNEL_V_2_6_38_8=y

CT_BINUTILS_V_2_21_1a=y

CT_CC_V_4_4_6=y

# CT_CC_GCC_USE_GRAPHITE is not set

CT_LIBC_EGLIBC_V_2_13=y

CT_DEBUG_gdb=y

# CT_GDB_GDBSERVER_STATIC is not set

CT_GDB_V_7_2a=y

CT_GMP_V_5_0_1=y

CT_MPFR_V_3_0_0=y

CT_TEST_SUITE_GCC=y