This branch (mkbootimg_tools) was made to host a relatively simple script I made that helps automate building boot images and boot image flashable zips for the Sony Xperia Z3 Compact, but can be adapted for other devices with no major changes.
Along with the script are provided the tools that actually manipulate with the boot image(s), as well as a compressed ramdisk that can be used to test the kernel's core functionality (assuming the device is indeed a z3c).