Orange Pi 4B build FIT image

[Eugene Parkhomenko]

I'm working on enabling secure boot on Orange Pi 4B.
So far I was able to burn eFuses, sign rk loader, a trust image, and a uboot image. To extend secure boot chain to the Linux Kernel, I've enabled FIT_SIGNATURE in u-boot, and manually built FIT image (Linux Kernel, initramfs(initrd), and a kernel DTB).
Now I want to add FIT image creation to the Armbian build system. What is the correct place/script to do it?