debian: Add hardening, recommended by lintian

Signed-off-by: Joachim Nilsson <[email protected]>

debian/rules

@@ -1,7 +1,12 @@
 #!/usr/bin/make -f           
+# export DH_VERBOSE=1
+export DEB_BUILD_MAINT_OPTIONS  = hardening=+all
+export DEB_CFLAGS_MAINT_APPEND  = -W -Wall -Wextra -O3
+export DEB_LDFLAGS_MAINT_APPEND = -Wl,--as-needed
 
-# Uncomment this to turn on verbose mode.
-#export DH_VERBOSE=1
+NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
+
+include /usr/share/dpkg/default.mk  # provides DEB_VERSION
 
 %:
 	dh $@ --with autoreconf