src-release.sh: Use -T0 for xz compression

Use parallel compression to create the xz archive.

On my machine (using 4 cores) this reduces the time to create
binutils-2.42.50.tar.xz from 1 minute 40 seconds to 56 seconds.

xz has supported -T0 since version 5.2.0 (released 2014-12-21).
1 file changed