Host machines with 4Gb physical memory are unable to build all images. During workiin on CI improvements it was noticed that runners with just 4Gb of memory are unable to create rootfs cache or make an images even that should be sufficient. Memory reservations are set very conservatively and we can keep that since adding a swap into the equation proves to be enough. If host machine is running Armbian (which will be in most cases) our ZRAM / ZSWAP memory management takes care of securing that extra needed memory.