cerbero package performance on android-universal: bzip2

During the package step on android bzip2 is used on a 1.8GB input tarfile/stream. This pegs a single core for multiple minutes.

I wonder how difficult it would be to use another bzip2 compression tool like lbzip2 here, which can make use of all cores, and still retains the same compression ratio:

• on gst-gitlab-htz-runner1 (32 vcpus): bzip2 -9 2m5s vs. lbzip2 -9 6.7s (on 1.8GB gstreamer-1.0-android-universal-1.15.2.tar)
• on gst-gitlab-htz-runner2 (48 cores): bzip2 -9 2m21s vs. lbzip2 -9 3.7s (on 1.8GB gstreamer-1.0-android-universal-1.15.2.tar)

Or maybe we should move to another compression like xz. xz --threads=48 -9 gstreamer-1.0-android-universal-1.15.2.tar takes just as long as the single-threaded bzip2 (ca. 2mins), but compresses better (364MB vs. 558MB). xz doesn't seem to want to make use of more than 8 cores though.

Not sure if it's worth it, just filing a bug for discussion.