debian: make the build reproducible

debian/rules

@@ -4,10 +4,10 @@ include /usr/share/dpkg/default.mk
 export DESTDIR=$(shell pwd)/debian/tmp
 
 %:
-	dh $@
+	dh $@ --with python3 --buildsystem=pybuild
 
 override_dh_auto_build:
-	make ui res translations
+	QT_HASH_SEED=0 make ui res translations
 	make python
 
 override_dh_auto_install:
@@ -15,4 +15,4 @@ override_dh_auto_install:
 	make install
 
 override_dh_install:
-	dh_install --fail-missing
+	dh_install --fail-missing