build fails while downloading external data file

It’s been a while since I’ve built VTK, and now I updated to 52157f40f47ce4f5be55f223258f1d7bfefcf60e and tried to build my squeaky clean clone of origin/master. I get a failure that some file cannot be downloaded:

-- Fetching ""
-- Fetching ""
CMake Error at /opt/cmake-3.14.2/share/cmake-3.14/Modules/ExternalData.cmake:1121 (message):

  not found at: ("Unsupported protocol") ("Unsupported protocol")

Your CMake doesn’t link against an OpenSSL-aware libcurl, so https:// URLs are not allowed. Please update/rebuild your CMake with SSL support.

Thanks for the swift reply!