cmake HAVE_M_C_ examples

WohlSoft/SDL-Mixer-X cmake/mixerx_macros.cmake :28

check_c_compiler_flag("${OPTFLAG}" HAVE_M_C_${OPT_VAR})

TheXTech/TheXTech cmake/build_props.cmake :76

check_c_compiler_flag("${OPTFLAG}" HAVE_M_C_${OPT_VAR})

WohlSoft/Moondust-Project _common/build_props.cmake :73

check_c_compiler_flag("${OPTFLAG}" HAVE_M_C_${OPT_VAR})