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_LOCAL_TARBALLS_DIR="${HOME}/src"

 CT_SAVE_TARBALLS=y

 CT_LOG_EXTRA=y

 CT_ARCH_ARCH="armv5te"

 CT_ARCH_CPU="arm926ej-s"

 CT_ARCH_TUNE="arm926ej-s"

 CT_ARCH_FLOAT_SW=y

 CT_ARCH_arm=y

 CT_TARGET_VENDOR="davinci"

 CT_KERNEL_linux=y

 CT_KERNEL_V_2_6_33_20=y

 CT_BINUTILS_V_2_20_1a=y

 CT_BINUTILS_FOR_TARGET=y

 CT_CC_V_4_3_2=y

 CT_CC_LANG_CXX=y

 CT_LIBC_glibc=y

 CT_LIBC_GLIBC_V_2_9=y

 # CT_LIBC_GLIBC_FORCE_UNWIND is not set

 CT_DEBUG_dmalloc=y

 CT_DEBUG_duma=y

 CT_DEBUG_gdb=y

 CT_GDB_NATIVE=y

 CT_GDB_V_6_8a=y

 CT_DEBUG_ltrace=y

 CT_DEBUG_strace=y

 CT_STRACE_V_4_5_19=y

 CT_GMP_V_4_3_2=y

 CT_MPFR_V_2_4_2=y