Make CMake 3.14 happy.
Make CMake 3.14 happy.

MichaelClerx/libcellml,hsorby/libcellml,nickerso/libcellml,hsorby/libcellml,cellml/libcellml,nickerso/libcellml,MichaelClerx/libcellml,cellml/libcellml,nickerso/libcellml,hsorby/libcellml,nickerso/libcellml,cellml/libcellml,hsorby/libcellml,MichaelClerx/libcellml,cellml/libcellml