764650: "zsh: FTBFS with noatime mounts (e.g. on reproducible builds armhf nodes)"
779566+: "zsh: Making the build reproducible"
Fixed in Git:
Blocked by: #778462
bin_sh_is_bash causes the config.h delta; see discussion on pkg-zsh-devel@ on 2016-12-20.
FTBFS on armhf are tracked in #764650
Our notes about issues affecting packages are stored in notes.git and are targeted at packages in Debian in 'unstable/amd64' (unless they say otherwise).