There were one error on the test (missing an s for --exists).
But we really need a recent zstd (1.4.0).
Thanks to Michal Privoznik to provide the right vension.

Signed-off-by: Juan Quintela <quintela@redhat.com>
Reported-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20200310111431.173151-1-quintela@redhat.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>