cmake HAVE_PPOLL examples

Lewuathe/mlir-hello thirdparty/llvm-project/lldb/cmake/modules/LLDBGenerateConfig.cmake :9 

check_symbol_exists(ppoll poll.h HAVE_PPOLL)

john30/ebusd CMakeLists.txt :75 

check_function_exists(ppoll HAVE_PPOLL)

ninja-build/ninja CMakeLists.txt :57 

check_cxx_symbol_exists(ppoll poll.h HAVE_PPOLL)