native: POSIX arch: Exclude unlikely code from coverage
native: POSIX arch: Exclude unlikely code from coverage

Some code in the POSIX arch core will only be executed
in some very atypical cases depending on the host load.
To avoid confusing developers, let's exclude it from the
coverage reports.

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

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