xz: Performance and compression tuning (V2) - fine tuning

xz: Performance and compression tuning (V2) - fine tuning

Changes since V1:

- Tuned some more 'tar'-command lines
- Included 'lfs/core-updates'
- Some fine-tuning

Hi,

Current results with V2 (clean builds):

'next':
'packages' => 255 MB
'ipfire-2.19.2gb-ext4.i586-full-core121.img.gz => 319 MB
'ipfire-2.19.i586-full-core121.iso' => 218 MB
Total => 792 MB

'xz-tuning':
'packages' => 228 MB
'ipfire-2.19.2gb-ext4.i586-full-core121.img.gz' => 318 MB
'ipfire-2.19.i586-full-core121.iso' => 207 MB

Total => 753 MB (-39 MB)

It would be nice if someone could review and test these. ;-)

If necessary, I can upload a complete patch.

Best,
Matthias

Signed-off-by: Matthias Fischer <matthias.fischer@ipfire.org>
Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>