debian: enable hardening flags, except PIE.

Enabling PIE currently results in the inability to build dynamic modules.

debian/rules

diff --git a/debian/rules b/debian/rules
index 09294c5..5068fdb 100755
--- a/debian/rules
+++ b/debian/rules
@@ -2,6 +2,8 @@
 
 #export DH_VERBOSE=1
 
+export DEB_BUILD_MAINT_OPTIONS=hardening=+all,-pie
+
 DPKG_EXPORT_BUILDFLAGS = 1
 include /usr/share/dpkg/buildflags.mk