Fetch all contrib packages at the same time

On the first try of fetching contrib packages, all downloads will start
at the same time. This should speed up the builds significantly.

If it fails, we will try again but not all at the same time. So the
errors should still be legible.

Change-Id: I2b45e1913eb2563350382c0ef1ed6fddf9f2ca05
Tuleap: #872

Makefile.packaging

@@ -54,7 +54,7 @@ $(RELEASE_TARBALL_FILENAME):
 	mkdir -p daemon/contrib/native
 	cd daemon/contrib/native && \
 	    ../bootstrap && \
-	    make fetch-all || make fetch-all || make fetch-all
+	    make fetch-all -j || make fetch-all || make fetch-all
 	rm -rf daemon/contrib/native
 
 	cd $(TMPDIR) && \