Remove -lidn2 from exported LIBS.
Do not propagate it from
isc-config.sh --libs isc.
When libidn2 support was added, AC_SEARCH_LIBS were used when --with-libidn2 is passed to configure. I missed that it adds this library to global LIBS, that would be later used for other projects from isc-config.sh. This request makes configure tests only local, without adding it global libraries.