Hi Andreas,
debian/rules does the following thing:
export CXXFLAGS:=$(shell dpkg-buildflags --get CXXFLAGS | sed 's/-fstack-protector *//')
This changes -fstack-protector-strong into -strong (which does not
exist).
You can do the same in a future-proof way with something like:
export DEB_BUILD_MAINT_OPTIONS = hardening=-stackprotector
HTH,
--
Etienne Millon