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

--- gcc-4.0.0/libstdc++-v3/configure-old	2005-04-30 22:04:48.061603912 -0500

+++ gcc-4.0.0/libstdc++-v3/configure	2005-04-30 22:06:13.678588152 -0500

@@ -7194,6 +7194,9 @@

 cat >>conftest.$ac_ext <<_ACEOF

 /* end confdefs.h.  */

 #include <complex.h>

+#ifdef __UCLIBC__

+#error ugly hack to make sure configure test fails here for cross until uClibc supports the complex funcs

+#endif

 int

 main ()

 {