cmake: Use same variable name as in standard FindOpenSSL script
cmake: Use same variable name as in standard FindOpenSSL script

Such variable used in civetweb compilation and should be set if later
one decides to migrate to OpenSSL version 1.1
root-mirror/root,root-mirror/root,karies/root,karies/root,karies/root,root-mirror/root,root-mirror/root,karies/root,karies/root,karies/root,olifre/root,olifre/root,olifre/root,root-mirror/root,karies/root,olifre/root,root-mirror/root,karies/root,karies/root,root-mirror/root,root-mirror/root,root-mirror/root,karies/root,root-mirror/root,olifre/root,root-mirror/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,karies/root,olifre/root