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

diff -dur strace-4.5.15.orig/signal.c strace-4.5.15/signal.c

--- strace-4.5.15.orig/signal.c	2007-01-11 23:08:38.000000000 +0100

+++ strace-4.5.15/signal.c	2007-07-14 19:24:43.000000000 +0200

@@ -1440,7 +1440,7 @@

 	  	tcp->u_rval = tcp->u_error = 0;

 		if(tcp->u_arg[0] == 0)

 		  	return 0;

-		tcp->auxstr = sprintsigmask("mask now ", tcp->u_arg[1]);

+		tcp->auxstr = sprintsigmask("mask now ", tcp->u_arg[1], 0);

 		return RVAL_NONE | RVAL_STR;

 	}

 	return 0;