libiconv: configure with --disable-nls

On Windows a build failure can be triggered during the
build of the static iconv if a dynamic iconv is already
present:

There's a circular dependency between libiconv and gettext
which (on a system with a dynamic gettext (and thus iconv)
installed in the system prefix) causes a failure to build
iconv.exe statically if it is built with nls ..

.. Which needs gettext
.. which depends on libiconv
.. so libtool finds a dynamically linked libgettext.la
.. and therefore presents ld with the dll import library
     libiconv.dll.a when linking iconv.exe
.. as well as the static libiconv.a that it has just built!
.. leading to multiply defined symbols from iconv.

Therefore, we build it without nls. If it later turns out
that we need it to be built with nls, then I will have to
build it in two passes (common practice when bootstrapping
GNU/Linux distros, MSYS2 and probably Cygwin and Homebrew).

Signed-off-by: Ray Donnelly <mingw.android@gmail.com>

scripts/build/companion_libs/320-libiconv.sh

@@ -102,6 +102,7 @@ do_libiconv_backend() {
         --build=${CT_BUILD}                                   \
         --host="${host}"                                      \
         --prefix="${prefix}"                                  \
+        --disable-nls                                         \
         "${extra_config[@]}"                                  \
 
     CT_DoLog EXTRA "Building libiconv"