makepkg.conf: use all possible threads for xz compression
Since version 5.4, xz always uses "multithreaded mode" for -T0
, making
its output reproducible. This means it is possible to add the option to
COMPRESSXZ
without causing reproducibility issues.
See https://git.tukaani.org/?p=xz.git;a=commitdiff;h=0adc13bfe32c14f3e4c6ce9f2d4fdf4112ab53f4