The practice of creating symbolic links is somewhat fragile. Always

The practice of creating symbolic links is somewhat fragile. Always
make copies instead.

There's too many times that we can't run the new binaries with old
libraries. Making the links when things are known to be 'safe' is a
nice optimization, but a copy of all the binaries is only 30MB, so
saving the copies at the cost of increased support when new symbols
are added and used as part of the bootstrap seems to be unwise.

There may be additional optimizations possible here, especially for
!FreeBSD hosts. However, that's beyond the scope of the problem I'm
trying to fix with make failing mid-way through an installworld across
change r363679. This optimization there caused us to run a new binary
with an old library once a new make was installed due to the symbolic
link. One could just copy make, but then other binaries fail as well,
so rather than play whack-a-mole, I opted to take us back to the old
way.  Before r340157 or so we did copies (thogh of a lot fewer
artifacts), and we didn't have issues like this.

Reviewed by: arichards@
Differential Revision: https://reviews.freebsd.org/D25967