Hi Lutz,
I didn't find way how to execute post-build after .hex file dump. I'll put feature request for S32DS - In my opinion the post-build step should be really "post-build".
As a workaround you can include hex file dump into your post build .bat file like this (I'm not sure if you are using ARM S32DS - for Power it is similar):
arm-none-eabi-objcopy -O ihex project.elf project.hex
your_post_build_commands
.
.
Jiri