Fail build script when build fails

Change-Id: Ic3a1573b57722a85b8df0d58c9fc39f1b8f46537
Reviewed-on: http://naan.mimuw.edu.pl:8001/90
Tested-by: Nebulostore Nebulostore <nebulostore@gmail.com>
Reviewed-by: Krzysztof Rzadca <krzadca@mimuw.edu.pl>
Tested-by: Krzysztof Rzadca <krzadca@mimuw.edu.pl>