Makefile: always use tags, so it's clear on top of which release is based

v0.6.4 is a lightway tag instead an annotated tag, so builds from git where
using 0.6.3 as prefix, when they where actually based on 0.6.4. Adding "--tags"
use the tags even if they are not annotated.
Merge pull request #145 from rata/master

Makefile: always use tags, so it's clear on top of which release is based