better zip compression (#6587)

Makefile

@@ -355,14 +355,16 @@ androidupdate: all
 	-rm $(INSTALL_DIR)/koreader/libs/libluajit.so
 
 	# assets are compressed manually and stored inside the APK.
-	cd $(INSTALL_DIR)/koreader && zip -r9 \
+	cd $(INSTALL_DIR)/koreader && 7z a -l -mx=9 -mfb=256 -mmt=on \
 		../../$(ANDROID_LAUNCHER_DIR)/assets/module/koreader-$(VERSION).zip * \
-		--exclude=*resources/fonts* \
-		--exclude=*resources/icons/src* \
-		--exclude=*share/man* \
-		--exclude=*spec* \
-		--exclude=*COPYING* \
-		--exclude=*README.md*
+		-xr!*resources/fonts* \
+		-xr!*resources/icons/src* \
+		-xr!*share/man* \
+		-xr!*spec$ \
+		-xr!*COPYING$ \
+		-xr!*README.md$ \
+		-xr!git$ \
+		-xr!gitiginore$ 
 
 	# make the android APK
 	$(MAKE) -C $(ANDROID_LAUNCHER_DIR) $(if $(KODEBUG), debug, release) \