make run/demo stop unexpectedly

[Sun Keqin]

Hi,
My colleague met a very strange problem today, so I ask for help.
There is an error when he run "make run/demo” in build directory, however, when he run "qemu-system-i386 -no-kvm -m 256 -serial mon:stdio -cdrom var/run/demo.iso" directly, it works successfully.
Do you know why it happened?  What should I do to fix that? 
Here is the details.

genode build completed
using fiasco kernel /home/jimmy/work/os/genode/build/kernel/fiasco.oc/fiasco
using sigma0/bootstrap at /home/jimmy/work/os/genode/build/l4
creating ISO image...
spawn qemu-system-i386 -no-kvm -m 256 -serial mon:stdio -cdrom var/run/demo.iso

L4 Bootstrapper
  Build: #1 2014: spawn id exp6 not open
    while executing
"expect {
		-i $running_spawn_id -re $wait_for_re { }
		eof     { puts stderr "Error: Spawned process died unexpectedly";   exit -3 }
		timeout { puts ..."
    (procedure "wait_for_output" line 11)
    invoked from within
"wait_for_output $wait_for_re $timeout_value $qemu_spawn_id"
    (procedure "spawn_qemu" line 51)
    invoked from within
"spawn_qemu $wait_for_re $timeout_value"
    (procedure "run_genode_until" line 18)
    invoked from within
"run_genode_until forever"
    (file "/home/jimmy/work/os/genode/genode-13.05/os/run/demo.run" line 139)
    invoked from within
"source $include_name"
    ("foreach" body line 3)
    invoked from within
"foreach include_name [get_cmd_arg --include ""] {
	puts "using run script $include_name"
	source $include_name
}"
    (file "/home/jimmy/work/os/genode/genode-13.05/tool/run" line 730)

Cheers,
keqin