cmake // build issue when OpenSSL enabled on Windows and schannel detected

[snikulov]

Options OpenSSL and Windows Schannel should be exclusive.
Enabling them both will break the build - we got redefinition in ssl_connect_data structure (ref to Appveyour buils).

So on Windows I disable CMAKE_USE_OPENSSL by default (Windows Schannel is preferred).
But we always can override this option with
cmake .. -DCMAKE_USE_OPENNSSL=ON | OFF

[mention-bot]

By analyzing the blame information on this pull request, we identified @jzakrzewski, @billhoffman and @Sukender to be potential reviewers

[snikulov]

@bradking Could you please review?

[bradking]

IIUC the goal is to present the CURL_WINDOWS_SSPI option (with default ON) when CMAKE_USE_OPENSSL is OFF (default). When CMAKE_USE_OPENSSL is ON then CURL_WINDOWS_SSPI should be non-optional and forced to OFF. In that case the dependent option should be:

  CMAKE_DEPENDENT_OPTION(CURL_WINDOWS_SSPI "Use windows libraries to allow NTLM authentication without openssl" ON
    "NOT CMAKE_USE_OPENSSL" OFF)

[snikulov]

@bradking updated per your comments with snikulov@b2e6d0a

If it looks OK for you - I'll squash it into single commit.

[bradking]

Yes, LGTM.

[snikulov]

@bagder I'm done.
CMake build for windows goes green again.

[bagder]

thanks!