Single-step create+compress in create_tarballs.sh

Currently, this script writes tarballs to disk before compressing them. Since disk I/O is not particularly fast on colchicifolium, and the uncompressed files are not needed, we should compress the tarballs before writing it to disk. This should allow the script to run faster by avoiding unneccessary disk I/O.

This may help fix tpo/tpa/team#40650 (closed)