Package Version script now deletes stale files when archiving packages.
Package Version script now deletes stale files when archiving packages.

Stale files seem to be causing havok on our buildbots, when old stale
archives exist package_version expects them to match the current
package. This CL will delete any stale files it finds when archiving
tar files.

BUG= https://code.google.com/p/nativeclient/issues/detail?id=3839
R=bradnelson@google.com

Review URL: https://codereview.chromium.org/269013007

git-svn-id: 721b910a23eff8a86f00c8fd261a7587cddf18f8@13144 fcba33aa-ac0c-11dd-b9e7-8d5594d729c2

sbc100/native_client,sbc100/native_client,sbc100/native_client,sbc100/native_client,sbc100/native_client,sbc100/native_client