Are you 100% sure about that. libSystem.dylib is a symlink to libSystem.B.dylib on systems I currently have access to.
Please ensure you have a backup and a means to boot your machine if your primary OS install fails to boot. People doing this kind of thing really worry me. I was also hoping to have you test with updated xzutils binaries without modifying your system.Actually I was able to find the library on Github.
Crap, I see I was too late posting this. There are instructions at https://www.makeuseof.com/tag/repair-ma ... mode-fsck/ might be of some assistance recovering your system - good luck.
I built with the 10.11 SDK - it should be extracted to your devkitpro folder. I've tested this locally on Mojave & High Sierra