ZeroMQ doesn't require libsodium, but will enable CURVE security if it's
available. This patch adds the optional dependency.
[Thomas: pass --without-libsodium explicitly when libsodium is not
enabled, and to achieve this, backport a patch from upstream zeromq.]
Signed-off-by: Frank Hunleth <fhunleth@troodon-software.com>
Reviewed-by: Romain Naour <romain.naour@openwide.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
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