I ran into the same issue building for Ubuntu. The root cause of the issue appears to be that CRYPTO_memcmp is defined in the OpenSSL packages available in the $DIST-security APT repository, but not the $DIST APT repository.
Adding the $DIST-security APT repository to APT sources and updating libssl-dev allowed ntpd to build. -- *Disclaimer: This e-mail and any attachments may contain confidential information. If you are not the intended recipient, any disclosure, copying, distribution or use of any information contained herein is strictly prohibited. * * * *If you have received this transmission in error, please immediately notify secur...@aptible.com <mailto:secur...@aptible.com> or call (866) 296-5003 and destroy the original transmission and any attachments without reading or saving.*
