softethervpn overrides nls.mk by defining its iconv functions. This only
works if the libc has iconv. In addition, it does not allow external
libiconv usage. TARGET_LDFLAGS is also the wrong place to add -liconv.
Signed-off-by: Rosen Penev <rosenp@gmail.com>
(cherry-picked from fb480e297c)
Rosen Penev