sanitycheck: make artifact cleanup for device-testing usable
sanitycheck: make artifact cleanup for device-testing usable

If we specify --device-testing and -M make it so that the resulting
artifacts are usable to run with device-testing again.  This means
keeping around the zephyr binary images (zephyr.{bin, hex, elf}) and
a few files so 'west' can function for flashing (CMakeCache.txt and
zephyr/runners.yaml).

Signed-off-by: Kumar Gala <a5e5248af4cd4f0ed8c515f61d40a6e2db46a66e@linaro.org>

Vudentz/zephyr,finikorg/zephyr,galak/zephyr,nashif/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,nashif/zephyr,Vudentz/zephyr,finikorg/zephyr,Vudentz/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,galak/zephyr,Vudentz/zephyr,nashif/zephyr,galak/zephyr,nashif/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,Vudentz/zephyr,finikorg/zephyr,nashif/zephyr