sanitycheck: Do not calculate size for native builds
sanitycheck: Do not calculate size for native builds

For native builds it does not make much sense to calculate
the size of the suposed RAM or ROM, or to check that new
unexpected sections did not appear.
So let's save the time and not do it.

Signed-off-by: Alberto Escolar Piedras <52be3174920ed06cbdfbcf9622a1a6c68e942617@oticon.com>

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