I've narrowed this down to the optimization for tree-vrp. Here is a patch which may be of interest ...
--- old/debian/rules 2014-09-09 13:55:04.000000000 -0600 +++ new/debian/rules 2015-05-08 09:00:40.307975277 -0600 @@ -6,8 +6,11 @@ DEB_HOST_GNU_TYPE ?= $(shell dpkg-architecture -qDEB_HOST_GNU_TYPE) DEB_BUILD_GNU_TYPE ?= $(shell dpkg-architecture -qDEB_BUILD_GNU_TYPE) -CFLAGS = -Wall -g -CFLAGS += -O2 +export DEB_BUILD_MAINT_OPTIONS = hardening=+all +DPKG_EXPORT_BUILDFLAGS = 1 +include /usr/share/dpkg/buildflags.mk + +CFLAGS += -Wall -fno-tree-vrp version=`ls src/.libs/lib*.so.* | \ awk '{if (match($$0,/[0-9]+\.[0-9]+\.[0-9]+$$/)) print substr($$0,RSTART)}'`