cmake HAVE_ISINF_IN_CMATH examples

llvm-dcpu16/llvm-dcpu16 cmake/config-ix.cmake :100 

check_symbol_exists(isinf cmath HAVE_ISINF_IN_CMATH)

KhronosGroup/SPIRV-LLVM cmake/config-ix.cmake :137 

check_symbol_exists(isinf cmath HAVE_ISINF_IN_CMATH)