Makefile.inc1: Restore adding tzsetup to _basic_bootstrap_tools

ITOOLS is only the list of programs to make a copy of during install, it
doesn't cause anything to be bootstrapped. Thus, by removing tzsetup
from _basic_bootstrap_tools, we end up without it on non-FreeBSD, and so
we error out trying to copy it to INSTALLTMP.

Note that _basic_bootstrap_tools is only used for BOOTSTRAP_ALL_TOOLS
(which is why zic was moved away from it). Should tzsetup evolve such
that the host version is insufficient on older FreeBSD it can be moved
to be more like zic, but that seems unnecessary for what is likely to
remain a simple tool.

This partially reverts commit 7a4a520064cb7fbff79560113682d6fe1a1ae9ee.

Fixes: 7a4a520064cb ("Fix cross-build from STABLE or older CURRENT.")