Try cmake 3.6

Author: dcwhite

Superbuild/CMakeLists.txt

@@ -24,7 +24,7 @@
 #  FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 #  DEALINGS IN THE SOFTWARE.
 
-CMAKE_MINIMUM_REQUIRED(VERSION 3.8 FATAL_ERROR)
+CMAKE_MINIMUM_REQUIRED(VERSION 3.6 FATAL_ERROR)
 
 IF(POLICY CMP0043)
   CMAKE_POLICY(SET CMP0043 OLD)