The reason is that on elfv2 systems we still have ld.bfd in base, but it's only used for 32-bit binaries (LLD currently doesn't support linking 32-bit PPC binaries).
ld.bfd from base supports only elfv1 and using it breaks linking many ports that set LLD_UNSAFE. Use Binutils from ports in such case.
PR: 239743
Submitted by: jbeich
Approved by: portmgr
Differential Revision: https://reviews.freebsd.org/D21996