This set of patch makes ports LLVM80 in sync with base LLVM80 as long https://reviews.freebsd.org/D20337 is accepted.
Actually this diff can completelly abandoned when llvm80 is updated to 8.0.1. The only remaining change not in 8.0.1 is the ABI name on target triple parsing, already in 9.0.0, but this is optional since we have an alternative (-mabi=elfv2) and we'll change the default ABI.
Regarding libunwind changes, libunwind is not part of ports LLVM, so it's not in this patch.
8.0.1 release is planned for jun 20, so I'm ok with abandoning this change in favor of updating ports directly in the next weeks.