Debian: migrate from DEB_BUILD_HARDENING to DEB_BUILD_MAINT_OPTIONS

Change-Id: Ic400c509ecd0c6e8485e9433f144528f6abc600d
diff --git a/debian/rules b/debian/rules
index cad7dfc..63ee1c3 100755
--- a/debian/rules
+++ b/debian/rules
@@ -5,7 +5,7 @@
 VERSION := $(shell echo '$(DEBVERS)' | sed -e 's/[+-].*//' -e 's/~//g')
 
 #export DH_VERBOSE=1
-export DEB_BUILD_HARDENING=1
+export DEB_BUILD_MAINT_OPTIONS = hardening=+all
 
 
 %: