Prevents the port from installing
<filename>charset.alias
</filename>. This must be installed only by
<package role="port">converters/libiconv
</package>.
<varname>CHARSETFIX_MAKEFILEIN
</varname> can be set to a path relative to
<varname>WRKSRC
</varname> if
<filename>charset.alias
</filename> is not installed by
<filename>${WRKSRC}/Makefile.in
</filename>.