This patch switches the compressor from Gzip to ZStandard for ssate cache
files.
Zstandard compression provides a significant improvement in
decompression speed as well as improvement in compression speed and disk
usage over the 'tgz' format in use. Furthermore, its configurable
compression level offers a trade-off between time spent compressing
sstate cache files and disk space used by those files. The reduced disk
usage also contributes to saving network traffic for those sharing their
sstate cache with others.
Zstandard should therefore be a good choice when:
* disk space is at a premium
* network speed / resources are limited
* the CI server can sstate packages can be created at high compression
* less CPU on the build server should be used for sstate decompression
Signed-off-by: Henry Kleynhans <hkleynhans@fb.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
