Building git darktable, and get: undefined reference to `SSLv3_client_method@OPENSSL_1_1_0'

I'm buiding git master darktable. A few days ago it started throwning this error: /usr/bin/ld: /usr/lib64/libcurl.so: undefined reference to `SSLv3_client_method@OPENSSL_1_1_0'

I'm building on slackware64-current. I don't get the error on a box which runs opensuse current. Any thoughts out there? I'm wondering if something in my build chain is finding some stale cruft related to curl, causing the hang.

?

John.