I have reverted the -z defs change in rawhide.  A substantial number of underlinked binaries are still shipped in rawhide after this change, either due to explicit overrides or incomplete build flags injection. This means that it is necessary to review built RPM packages for incorrectly linked binaries even after the change.  Considering that -z defs also causes a lot of spurious build failures, it's probably not the way to go.

(The work to enable -z defs is not lost—even after the revert, packages which have been fixed so far will remain fixed.)