While macOS Sierra is not officially supported for deploying the new VCSA for vSphere 6.5, most folks have had no issues installing/upgrading on it. However, I was not one of those lucky ones and ran into an error about halfway through the installation process “Error: ovftool is not available” was the error message and would not let me pick the size of the new to deploy OVA.
Reading through the logs you will see something like this: 2016-11-17T00:33:11.992Z – error: could not find ovftoolCmd: /private/var/folders/lt/w4dsqrqn02x0h26k6vmwdtq40000gn/T/AppTranslocation/vcsa/ovftool/mac/ovftool
The quick fix is to simply copy the entire vcsa folder on the ISO into whatever directory is listed in your error log. Once you copy that entire folder (Which has the ovftool and the ova file) it should continue with no issues.
Kix's Blog 