tar task should create a folder

Hi,

It's me again :)

Similar issue but different task...
It is similar to zip task issue you guys have fixed last time.

The issue is with destfile attribute of tar task.
<tar destfile="${root.dir}/${archive}/test.tar.gz">

When the task is excuted, the task doesn't create the
${root.dir}/${archive} folder structure and fail, unless the structure is
already there.
Sometime, users want to put the final tar.gz file in a different folder.
Otherwise one has to use mkdir to create the dir structure first then call
the tar task.