Use unzip -DD

We put reproducible timestamps in zip files so that the artifacts
are consistent, but that leads to old timestamps in the output
directory if they are unzipped as part of the build.  Use
unzip -DD when unzipping to update the timestamps.

Bug: 161015009
Test: touch -d 2020-01-01 ref; find $OUT/system -not -newer ref
Change-Id: I6f08ba8695d90a8225cfc04e679755e6296deed0