Buildworld error

Hi, I recently forked FreeBSD 13 from github and debranded what I could find, when I went to build it using make -j2 buildworld KERNCONF=MODEDKERNEL -DNO_CLEAN . It errors out with libunwind and when building the dependencies using make depend it errors out saying it cannot find llvm-tblgen. Any help is welcomed, thank you.
You are violating the BSD license by removing the FreeBSD copyright message from the source. Read careful the copyright of the code and remove/delete your project before you get into legal troubles.

How and I put the copy right notice back in, thanks for the advice.
It's written directly there in the two clauses. With BSD-licensed code, you can do almost whatever you want, freely modify it, add your own terms to your distribution, add your own copyright notice (applicable to your changes), use it in commercial products, ..., virtually anything you can't do with GPL-licensed code, but you are always required to retain the original copyright notice and terms of the license (or reproduce it somewhere, e.g. for commercial products in their docs).

I think this just translates to a basic rule of decency, when you use others' work (for free!), give proper credit.