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_ARCH="mips1"

CT_ARCH_FLOAT_SW=y

CT_ARCH_mips=y

CT_KERNEL_linux=y

CT_KERNEL_V_3_0_30=y

CT_BINUTILS_V_2_21_1a=y

CT_CC_V_4_6_1=y

CT_CC_LANG_FORTRAN=y

CT_CC_LANG_CXX=y

CT_LIBC_uClibc=y

CT_LIBC_UCLIBC_V_0_9_32=y

CT_LIBC_UCLIBC_CONFIG_FILE="${CT_LIB_DIR}/samples/${CT_TARGET}/${CT_LIBC}-${CT_LIBC_VERSION}.config"

CT_LIBC_UCLIBC_WCHAR=y

CT_DEBUG_dmalloc=y

CT_DEBUG_duma=y

CT_DEBUG_gdb=y

CT_GDB_NATIVE=y

CT_GDB_NATIVE_STATIC=y

CT_GDB_V_7_2a=y

CT_MPFR_V_3_0_1=y