Put paths into find_program call for makensis.
Put paths into find_program call for makensis.

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