remove SmartOS specific ENV variables
ensure embedded ncurses wins in the LD search path

Creating this symlink ensures Omnibus-compiled embedded nurses wins when
the linker is looking for libcurses.so.1. In particular we are trying to
fake out the Ruby readline extension by letting -ltermcap resolve to
libcurses.so.1.
`--enable-overwrite` to force symlink from curses to ncurses