Hi, @ofer-bahar-guardknox , Very sorry for replying late.
The VARIANT-POST-BUILD
Pre-compile and Post-build options
It is AUTOSAR specific option.
https://www.autosar.org/fileadmin/standards/R4-3/CP/AUTOSAR_EXP_LayeredSoftwareArchitecture.pdf
Now, for the understanding POST build steps
---------------------------------------------------------------
1. How to Select your project see the option for adding command at
Please go to as screenshot below
Properties -> Settings -> Build steps -> Post build-steps
and write command at
command :

Now, you also need to understand that, command that you enter POST build steps check box, will be added to the makefile which will be specifying the operations to perform POST building the .elf file
So in the below two screenshots you can see that
1. echo command has been entered into command section, and then

2. the echo command is put in the makefile

You can also first try using echo command and printing the test message to be sure that it is working.
Similarly, You can add the "Valid" command in the POST -build section for your requirement.
Please let us know if you have any further question .
Thank you, Kind regards,
- Mehul Patel