Whilst working on the Reproducible Builds effort [0], we noticed
that zstd could not be built reproducibly.
This is due to the manual page encoding the number of CPUs from the
build machine and thus varies across builds.
This was originally filed in Debian as #897904 [1].
[0] https://reproducible-builds.org/
[1] https://bugs.debian.org/897904
Signed-off-by: Chris Lamb <lamby@debian.org>
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