ENH: Add configure time check that CMake supports HTTPS
Created by: msmolens
Some build targets require downloading files using the HTTPS protocol. Before this commit, targets such as 'python-source' would fail during the build process with errors like:
CMake Error at python-source-prefix/src/python-source-stamp/download-python-source.cmake:27 (message):
error: downloading
'https://www.python.org/ftp/python/2.7.11/Python-2.7.11.tgz' failed
status_code: 1
status_string: "Unsupported protocol"
log: Protocol "https" not supported or disabled in libcurl
This commit adds a configure-time check that CMake supports HTTPS. Now, developers are made aware of the problem before building.
If CMake doesn't support HTTPS, the configuration step now fails with a descriptive error message and a suggested solution:
CMake Error at CMake/SlicerCheckCMakeHTTPS.cmake:21 (message):
error: This CMake does not support the HTTPS protocol. Ensure that CMake
is compiled with CMAKE_USE_OPENSSL enabled.