- Re-cloned zonemaster-ldns with --recurse-submodules so the bundled
ldns C library source (including Changelog and configure.ac) is present
- Added autoconf, automake, libtool to Dockerfile.backend ldns-build stage
so libtoolize + autoreconf can generate ldns/configure during make
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
