Flag to indicate that entry name should be formatted
according to GNU tar extension if an attempt is made
to write an entry that exceeds the 100 char POSIX
limit.
Throws an Exception if extra data cannot be parsed into extra fields.
setExtra() -
Method in class org.apache.commons.compress.archivers.zip.ZipEntry
Unfortunately java.util.zip.ZipOutputStream seems to access the extra data directly,
so overriding getExtra doesn't help - we need to modify super's data
directly.