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_LOCAL_TARBALLS_DIR="${HOME}/src"

 CT_SAVE_TARBALLS=y

 CT_LOG_EXTRA=y

 CT_ARCH_LE=y

 CT_ARCH_FLOAT_SW=y

 CT_ARCH_mips=y

 CT_TARGET_VENDOR="sde"

 CT_BINUTILS_V_2_21_1a=y

 CT_CC_V_4_4_6=y

 # CT_CC_GCC_ENABLE_TARGET_OPTSPACE is not set

 CT_LIBC_none=y

 CT_DEBUG_gdb=y

 CT_GDB_V_6_8a=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