cc/gcc: modify to build gcc-4.8-based cross-tools

Building cross-tool based on gcc-4.8 fails while "Installing
pass-2 core C compiler", because building libgcc.mvars needs
libbacktrace.a that gcc.sh doesn't build. This patch inserts
a few lines configuring, and making libbacktrace into gcc.sh
to build gcc-4.8-based cross-tools successfully.

Reported-by: Plotnikov Dmitry <leitz@ispras.ru>
Signed-off-by: Jongsung Kim <neidhard.kim@lge.com>
Message-Id: <201305031831.33395.neidhard.kim@lge.com>
Patchwork-Id: 241258

CT_EXPERIMENTAL=y

CT_LOCAL_TARBALLS_DIR="${HOME}/src"

CT_SAVE_TARBALLS=y

CT_PATCH_NONE=y

CT_LOG_EXTRA=y

CT_ARCH_64=y

CT_ARCH_s390=y

CT_KERNEL_linux=y

CT_KERNEL_V_2_6_31=y

CT_BINUTILS_V_2_19_1a=y

CT_CC_V_4_4_5=y

CT_CC_LANG_CXX=y

CT_LIBC_glibc=y

CT_LIBC_GLIBC_V_2_9=y

CT_GMP_V_4_3_2=y

CT_MPFR_V_2_4_2=y

CT_PPL_V_0_10_2=y

CT_CLOOG_V_0_15_10=y