twister: passing the build dir to device serial pty
twister: passing the build dir to device serial pty

Passing the zephyr build directory to the script run by
--device-serial-pty, it makes the feature of the device serial
pty more flexible.

Signed-off-by: Enjia Mai <7a2de2448a1c31432e87f79c5f6556ebbe33f656@intel.com>

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