Partially revert r403755. It can't build the curses module against ncurses from
ports. It probably can, but configure is too smart to figure that out.

I have no confidence that linking against curses from ports results in a properly
working zshell. So, for now, back out the change. It will build a shared lib zsh
against ncurses from ports, but breaks statically-linked zsh's. Mark the port
as IGNORE if we're using ncurses from ports and building a static zsh.

Also, remove a regression-test target that isn't useful anymore (thanks to bapt
for the reminder about this).

I am not enthused about this change. It doesn't really "fix" the below PR, so
much as shoot ourselves in the other foot instead.

PR: 205500