build bionic libc tests as part of system image

Change-Id: Ie8cdd07d2b82c37446a58d1ddaedceef45d7f407
Signed-off-by: Amit Pundir <amit.pundir@linaro.org>
update how we run test_system test

Change-Id: I25e6251f83dd90610f67408d1c9522b16fa380dd
Signed-off-by: Amit Pundir <amit.pundir@linaro.org>