scripts/gdb: If not building expat for gdb, disable

--with-expat=yes is unconditionally passed to the gdb configure
stage, instead of respecting the ${do_expat} decision.

Disable if not needed. Prevents error building canadian cross;

configure: error: expat is missing or unusable

Where configure stage fails to find expat on the host compiler.

Signed-off-by: "David Holsgrove" <david.holsgrove@xilinx.com>
Signed-off-by: Bryan Hundven <bryanhundven@gmail.com>
Message-Id: <4c4410a2a8aab24a29c5.1349244128@localhost.localdomain>
PatchWork-Id: 188711

CT_EXPERIMENTAL=y

CT_LOCAL_TARBALLS_DIR="${HOME}/src"

CT_SAVE_TARBALLS=y

CT_LOG_EXTRA=y

CT_ARCH_CPU="ev56"

CT_ARCH_TUNE="ev56"

CT_ARCH_ALPHA_EV67=y

CT_KERNEL_linux=y

CT_KERNEL_V_2_6_38_8=y

CT_BINUTILS_V_2_21_1a=y

CT_CC_V_4_3_5=y

CT_CC_LANG_FORTRAN=y

CT_CC_LANG_CXX=y

# CT_CC_GCC_ENABLE_TARGET_OPTSPACE is not set

CT_LIBC_glibc=y

CT_LIBC_GLIBC_V_2_13=y

CT_LIBC_EXTRA_CC_ARGS="-Wl,--no-relax"

CT_LIBC_GLIBC_USE_PORTS=y

CT_GMP_V_5_0_1=y

CT_MPFR_V_3_0_0=y