Create symlinks to host tools on non-FreeBSD hosts

This is unnecessary when cross-building from Linux/macOS.
Additionally, cp -p appears to be broken on macOS Big Sur
(https://openradar.appspot.com/8957219).

For some unknown reason this commit appears to fix
freezes when building on macOS Big Sur.
This also fixes building in docker with volume mounts
with ACLs, since setting the ACL with cp -p fails otherwise.

Obtained From: CheriBSD
Tested By: gnn (macOS Big Sur), Nathaniel Wesley Filardo (docker)
Reviewed By: jrtc27, imp
Differential Revision: https://reviews.freebsd.org/D28267