qisys.archive: Add 'flat' feature to tar archive creation.
qisys.archive: Add 'flat' feature to tar archive creation.

The compress method has a flat option that enables the creation of flat
archive (ie. archive that does not have a top directory).

This option is only implemented for zip archives.

This commit implements the 'flat' feature for the tar archive.

Change-Id: Ic553b0fcc607e4ef9e1ff7609cbe8c50f9c63b71
Reviewed-on: http://gerrit.aldebaran.lan/77845
Tested-by: gerrit
Reviewed-by: hkouki <59709db2b0e3af4007fe82139267affb778dfd8b@aldebaran-robotics.com>
Tested-by: hkouki <59709db2b0e3af4007fe82139267affb778dfd8b@aldebaran-robotics.com>

aldebaran/qibuild,aldebaran/qibuild,aldebaran/qibuild,aldebaran/qibuild