[PERFORMANCE] compression speedup for multiple project sharing

Instead of creating a Zip file for every project which is again zipped
to into the final Zip file only one file will be created. This should
avoid compressing data twice if multiple projects are shared at the same
time.


Change-Id: Ie1e31930323031cc02b19e8ffc3aae87d85c68c5
Reviewed-on: http://saros-build.imp.fu-berlin.de/gerrit/1538
Tested-by: Jenkins CI
Reviewed-by: Stefan Rossbach <srossbach@arcor.de>