Ramalama
Well the build system is IMHO really good if you compare it to others I've seen when digging through emulation related stuff but it's also the result of years of incremental improvements and guys like milhouse did an outstanding job (I hope he's well whereever he is right now!), don't forget all others who also wrote great stuff of course: Contributors to LibreELEC/LibreELEC.tv · GitHub the list is full of "nerds" sharing their expertise which is great.
In the end you only have to clone the repo, change one line, type in make image and you're done. Everything else is just to pass some infos to the image naming scheme or for identifikation purposes so you know the name of the image you're running.
About the kernel... well unless you don't want to slim it down to a point where it would only run on your system there is not much to do... the kernel conf is regularly updated and adjusted to only builds stuff a distro like LE really needs.
All error where linked to gdk-pixbuf so far so I guess it should be fine once it is in place on your host machine.