Makefile.inc1: Support building with macOS Ventura's AMFI Launch Constraints

As of macOS Ventura, Apple-signed binaries cannot be run if copied away from
their system location. This security feature doesn't really make sense for
boring things like sh(1), more so for applications with special entitlements,
but it's universally present, and results in the following error:

>>> Install check world
bmake[2]: "/Users/Jess/cheri/freebsd/Makefile.inc1" line 572: warning: "MAKEFLAGS= CPUTYPE=dummy /Users/Jess/cheri/build/freebsd-riscv64-build/bmake-install/bin/bmake -f /dev/null  -m /Users/Jess/cheri/freebsd/share/mk MK_AUTO_OBJ=no -V CPUTYPE" exited on a signal
bmake[2]: "/Users/Jess/cheri/freebsd/Makefile.inc1" line 575: CPUTYPE global should be set with ?=.

As with host-symlinks, we don't actually need to copy the files on macOS, since
we're not updating the current machine, so copy its approach and just symlink
them instead.

MFC after: 1 week

(cherry picked from commit dda4d97289f17aa8b2bbfd8d63a746b3a7836fd5)