arch/sparc: add absic support

Add support for building SPARC targeted toolchain.
With this patch I have built a working sparc V8 (32 toolchain).

Testing shows that not all gcc versions works well:
4.4.1 OK (kernel builds and the final kernel can boot)
4.4.2 Not tested
4.4.3 Not tested
4.4.4 BAD (Kernel can build but fails during boot)
4.4.5 BAD (Kernel can build but fails during boot)
4.5.1 BAD (Build fails with a spill related ICE - http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35664)
4.5.2 OK (kernel builds and boots)

I have successfully been using the 4.5.2 version for a few months.

This patch does not add support for the LEON variant.
That may come later.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
[yann.morin.1998@anciens.enib.fr: for 32-bit, default CT_TARGET_ARCH is OK]
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>

# Compute powerpc-specific values

CT_DoArchTupleValues () {

    # The architecture part of the tuple, override only for 64-bit

    if [ "${CT_ARCH_64}" = "y" ]; then

        CT_TARGET_ARCH="powerpc64"

    fi

    # Add spe in the tuple if needed

    case "${CT_LIBC},${CT_ARCH_POWERPC_SPE}" in

        glibc,|eglibc,)   CT_TARGET_SYS=gnu;;

        glibc,y|eglibc,y) CT_TARGET_SYS=gnuspe;;

    esac

    # Add extra flags for SPE if needed

    if [ "${CT_ARCH_POWERPC_SPE}" = "y" ]; then

        CT_ARCH_TARGET_CFLAGS="-mabi=spe -mspe"

        CT_ARCH_CC_CORE_EXTRA_CONFIG="--enable-e500_double"

        CT_ARCH_CC_EXTRA_CONFIG="--enable-e500_double"

    fi

}