debian/rules: Only export hardening related building HOST_/EXTRA flags when dpkg...

On newer dpkg-dev versions, dpkg-buildflags handle them directly and are
injected by gcc (6.x).

Change-Id: I1fd99405d9b07e10c3bc41034256212ebeaf7549
Signed-off-by: Santiago <santiagorr@riseup.net>

diff --git a/debian/rules b/debian/rules
index b652adc..3ef1c66 100755 (executable)
--- a/debian/rules
+++ b/debian/rules
@@ -15,20 +15,26 @@ DEB_HOST_GNU_CPU := $(shell dpkg-architecture -qDEB_HOST_GNU_CPU)
 export DEB_BUILD_MAINT_OPTIONS = hardening=+all,-pie
 
 # see ENVIRONMENT in dpkg-buildflags(1)
-# package maintainers to append CFLAGS
-export DEB_CFLAGS_MAINT_APPEND  = -fPIC
-# package maintainers to append LDFLAGS
-#export DEB_LDFLAGS_MAINT_APPEND = -Wl,--as-needed
-
+DPKG_EXPORT_BUILDFLAGS = 1
 include /usr/share/dpkg/buildflags.mk
-export EXTRA_CFLAGS=$(CFLAGS)
-export EXTRA_CPPFLAGS=$(CPPFLAGS)
-export HOST_EXTRA_CFLAGS=$(CFLAGS)
-export HOST_EXTRA_CPPFLAGS=$(CPPFLAGS)
-# need to be stripped as DPDK build system adds them and it would be -Wl,-Wl,opt
-export EXTRA_LDFLAGS=$(shell echo $(LDFLAGS) | sed 's/-Wl,//g')
-# HOST_CC build system does not add -Wl ...
-export EXTRA_HOST_LDFLAGS=$(LDFLAGS)
+
+# Support backporting to jessie
+dpkg_version_lt = $(shell dpkg --compare-versions $$(dpkg --status dpkg-dev | grep Version | cut -d' ' -f2) lt-nl "1.18.11" && echo yes)
+ifeq (yes, $(dpkg_version_lt))
+       # package maintainers to append CFLAGS
+       # For Debian, dpkg-dev >= 1.18.11 and gcc 6.x, dpkg-buildflags and gcc
+       # handle -fPIC and related flags relying on specs files
+       # (/usr/share/dpkg/*specs)
+       export DEB_CFLAGS_MAINT_APPEND  = -fPIC
+       export EXTRA_CFLAGS=$(CFLAGS)
+       export EXTRA_CPPFLAGS=$(CPPFLAGS)
+       export HOST_EXTRA_CFLAGS=$(CFLAGS)
+       export HOST_EXTRA_CPPFLAGS=$(CPPFLAGS)
+       # need to be stripped as DPDK build system adds them and it would be -Wl,-Wl,opt
+       export EXTRA_LDFLAGS=$(shell echo $(LDFLAGS) | sed 's/-Wl,//g')
+       # HOST_CC build system does not add -Wl ...
+       export EXTRA_HOST_LDFLAGS=$(LDFLAGS)
+endif
 
 export RTE_DEVEL_BUILD=n