CMake: replaced obsolete use of add_compiler_export_flags() function (#72).
CMake: replaced obsolete use of add_compiler_export_flags() function (#72).

cellml/libcellml,hsorby/libcellml,cellml/libcellml,libcellml/buildbot-testing,libcellml/buildbot-testing,cellml/libcellml,nickerso/libcellml,MichaelClerx/libcellml,nickerso/libcellml,hsorby/libcellml,hsorby/libcellml,cellml/libcellml,MichaelClerx/libcellml,nickerso/libcellml,MichaelClerx/libcellml,hsorby/libcellml,nickerso/libcellml