By default the dos2unix build uses the msgfmt application which is
provided by the host tool gettext in OpenWrt. Instead of adding the
dependency to gettext deactivate NLS support.
This fixes the following build error:
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msgfmt -c po/da.po -o po/da.mo
make[4]: msgfmt: No such file or directory
make[4]: *** [Makefile:472: po/da.mo] Error 127