Share the debian13 patch content, renamed to libevent-libdir-install.patch,
so the install directory follows CMAKE_INSTALL_LIBDIR instead of a
hardcoded lib64. On Rocky Linux GNUInstallDirs already defaults it to
lib64, so the Dockerfile does not need to pass it.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
