XeBuild uses specific bootloader files to build glitch images (the filenames and CRCs for each file are stored in a .ini file which is parsed to check that the files exist).
If the .ini file isn't present for the kernel version you want to build an image for, J-Runner will throw an error.
At the moment, there is no need for the latest kernel version (there is an unofficial way to do it, but until an updated version of DashLaunch is released, you don't need to update).