test: unittest: run for 32bit architecture
test: unittest: run for 32bit architecture

Running tests compiled for 64bit architecture were causing errors
in logger module. Updated unittest.cmake to build tests only
for 32bit architecture.

Signed-off-by: Jakub Rzeszutko <db01fea5b4491dba4fc272e7096cf665c7b907b9@nordicsemi.no>

galak/zephyr,explora26/zephyr,GiulianoFranchetto/zephyr,GiulianoFranchetto/zephyr,galak/zephyr,nashif/zephyr,GiulianoFranchetto/zephyr,punitvara/zephyr,punitvara/zephyr,Vudentz/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,GiulianoFranchetto/zephyr,Vudentz/zephyr,galak/zephyr,Vudentz/zephyr,ldts/zephyr,punitvara/zephyr,punitvara/zephyr,ldts/zephyr,finikorg/zephyr,explora26/zephyr,galak/zephyr,explora26/zephyr,finikorg/zephyr,punitvara/zephyr,nashif/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,explora26/zephyr,finikorg/zephyr,Vudentz/zephyr,ldts/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,ldts/zephyr,nashif/zephyr,explora26/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,nashif/zephyr,nashif/zephyr,zephyrproject-rtos/zephyr,GiulianoFranchetto/zephyr,ldts/zephyr