add -fno-stack-protector to supress __strict build error observed on ubuntu12.04...

add -fno-stack-protector to supress __strict build error observed on ubuntu12.04 x86_64 bit machine for me.

Simple "make" gave me this -
jailhouse/hypervisor/printk.o: In function `hex2str':
jailhouse/hypervisor/printk-core.c:90: undefined reference to `__stack_chk_fail'
jailhouse/hypervisor/printk.o: In function `__vprintk':
jailhouse/hypervisor/printk-core.c:200: undefined reference to `__stack_chk_fail'

Signed-off-by: santosh shukla <santosh.shukla@linaro.org>
[Jan: rewrap to respect 80 chars limit]
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>