debian: Enable all hardening flags

Starting with gcc-5 there is no performance loss when enabling PIE on
i386, so there is no point in not enabling it.

Ref: https://software.intel.com/en-us/blogs/2014/12/26/new-optimizations-for-x86-in-upcoming-gcc-50-32bit-pic-mode

debian/changelog

@@ -92,6 +92,9 @@ dpkg (1.18.5) UNRELEASED; urgency=medium
     - Add a configuration summary to configure output.
     - Make git log invocation immune to local configuration.
     - Do not require passing the perl interpreter to run-script.
+  * Packaging:
+    - Enable all hardening flags, starting with gcc-5 there is no performance
+      loss anymore when enabling PIE on i386.
   * Test suite:
     - Add a unit test to compile perl code with warnings.
     - Add a unit test for the trigger deferred parser.

debian/rules

@@ -8,11 +8,11 @@ WFLAGS := -Wall -Wextra -Wno-unused-parameter -Wno-missing-field-initializers
 # XXX: Stack Protector Strong is only available in gcc >= 4.9
 cc_version = $(shell $(CC) -dumpversion 2>/dev/null)
 cc_version_lt = $(shell dpkg --compare-versions "$(cc_version)" lt-nl "$(1)" && echo yes)
-hardening_old = DEB_BUILD_MAINT_OPTIONS="hardening=-stackprotectorstrong"
+hardening_old = $(if $(call cc_version_lt,4.9),-stackprotectorstrong)
 
 # Use the in-tree dpkg-buildflags
 dpkg_buildflags = \
-	$(if $(call cc_version_lt,4.9),$(hardening_old)) \
+	DEB_BUILD_MAINT_OPTIONS="hardening=+all,$(hardening_old)" \
 	DEB_CFLAGS_MAINT_APPEND="$(WFLAGS)" \
 	DEB_CXXFLAGS_MAINT_APPEND="$(WFLAGS)" \
 	$(CURDIR)/run-script scripts/dpkg-buildflags.pl