Java fails to unzip archives created by archive/zip because directories are
written with the "data descriptor" flag (bit 3) set, but emits no such
descriptor. To fix this, we explicitly clear the flag.

Fixes #25215

Change-Id: Id3af4c7f863758197063df879717c1710f86c0e5
Reviewed-on: https://go-review.googlesource.com/110795Reviewed-by: Joe Tsai <thebrokentoaster@gmail.com>
Run-TryBot: Joe Tsai <thebrokentoaster@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>