* Andreas Tille <andreas@an3as.eu>, 2015-12-17, 19:11:
override_dh_auto_build: + if mount | grep "^proc " ; then echo "proc mounted - fine"; else mount proc /proc -t proc ; fi
Well, you need root privileges to mount /proc, so doing it in debian/rules almost certainly won't work.
If /proc is not mounted in your build environment, then you need to fix the environment. There's nothing that can be done about it in debian/rules.
-- Jakub Wilk