archive_write_disk_{posix,windows}.c: Don't modify attributes for existing directorie...

archive_write_disk_{posix,windows}.c: Don't modify attributes for existing directories when ARCHIVE_EXTRACT_NO_OVERWRITE is set

Enables unpacking multiple archives into a single directory whose permissions,
owner, and other attributes are pre-configured or otherwise determined ahead
of time by a single archive without the need to repeat the same attributes in
every archive, such as in package installation scenarios.

Signed-off-by: Paul Spangler <paul.spangler@ni.com>