macOS - Build cURL with SSH Support
Nov 17, 2016

The version of cURL that comes with macOS does not contain libssh2 support; nor does the one from Homebrew. That is of course unless you specifically tell it to build with libssh2 support.

brew install libssh2 && brew install curl --with-libssh2

For cmake:

CURL_LIBRARY=/usr/local/opt/curl/lib/libcurl.a CURL_INCLUDE_DIR=/usr/local/opt/curl/include cmake