Make HAVE_COVERAGE visible when not building for emscripten.
Make HAVE_COVERAGE visible when not building for emscripten.

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