cmake HAVE_ISNAN_IN_MATH_H examples

llvm-dcpu16/llvm-dcpu16 cmake/config-ix.cmake :104 

check_symbol_exists(isnan math.h HAVE_ISNAN_IN_MATH_H)

KhronosGroup/SPIRV-LLVM cmake/config-ix.cmake :141 

check_symbol_exists(isnan math.h HAVE_ISNAN_IN_MATH_H)