Your package fails to build with the newest upcoming autoconf-2.71, which is part of a wide Fedora change. Please see the attached copr: https://copr.fedorainfracloud.org/coprs/odubaj/autoconf-2.70/packages/. More information about testing your package when building with autoconf available here: https://fedoraproject.org/wiki/Changes/Autoconf_271#How_To_Test
autoconf-2.71 works fine for me on three machines: f35/rawhide, f34/rawhide (pre-branch), f34 post-branch. E.g.: $ rpm -q autoconf autoconf-2.71-1.fc34.noarch $ rpmbuild -ba SPECS/ceph.spec ... + /usr/bin/rm -rf /home/kkeithle/rpmbuild/BUILDROOT/ceph-16.1.0-0.8.snapshot.fc34.x86_64 + RPM_EC=0 ++ jobs -p + exit 0 1) ceph doesn't use autoconf (see the .spec file ;-)) 2) your copr build's build.log.gz is truncated 3) ceph builds take a lot of disk and memory. In all likelihood your builds failed because of one of those issues, not because of the new autoconf. And as another data point, I can remove autoconf entirely (and install libtool with `rpm -i --nodeps libtool-2.4.6-40.fc34.x86_64.rpm`) and build successfully. I strongly suggest you configure your copr builds with more disk (~50G is what I have found to be needed, YMMV) and 12G memory minimum.