xz to produce base.tar.xz fails in low mem/cpu environment fails

Hi all,

After some troubleshooting where the build would fail for me (see https://bbs.archlinux.org/viewtopic.php?pid=2024067#p2024067), I found that xz is failing to produce the base.tar.xz file. Removing -T0 appears to fix the issue, though it can take quiet a while for the compression to complete, leaving -T0 and removing -9 also appears to fix the issue.

I'm attempting to build this container in a VM with 4 cores & 2 GB memory, though the amount of memory that's available to the build process would likely be far less as i'm running other applications as well.

Using zstd might be a good option instead of using xz here. Perhapes adding -v to the xz command may help show the progress at the very least if it's taking a while to complete.