cc/gcc: add option to compile against static libstdc++, for gcc-4.4 and newer

Idea and know-how taken from CodeSourcery build script.

Normal build:
$ ldd arm-unknown-linux-uclibcgnueabi-gcc
linux-gate.so.1 => (0xb77f3000)
libstdc++.so.6 => /usr/lib/libstdc++.so.6 (0xb76e8000)
libc.so.6 => /lib/i686/cmov/libc.so.6 (0xb75a1000)
libm.so.6 => /lib/i686/cmov/libm.so.6 (0xb757a000)
/lib/ld-linux.so.2 (0xb77f4000)
libgcc_s.so.1 => /lib/libgcc_s.so.1 (0xb755c000)

CC_STATIC_LIBSTDCXX=y:
$ ldd arm-unknown-linux-uclibcgnueabi-gcc
linux-gate.so.1 => (0xb7843000)
libc.so.6 => /lib/i686/cmov/libc.so.6 (0xb76e6000)
/lib/ld-linux.so.2 (0xb7844000)

I made CC_STATIC_LIBSTDCXX default=y since I think
it is always desirable.

Signed-off-by: Johannes Stezenbach <js@sig21.net>

 # 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

 }