cmake HAVE_STD_FUTURE examples

nghttp2/nghttp2 CMakeLists.txt :142 

check_cxx_source_compiles("
  #include <vector>
  #include <future>
  int main() { std::vector<std::future<int>> v; }" HAVE_STD_FUTURE)

fluent/fluent-bit lib/nghttp2-1.65.0/CMakeLists.txt :159 

check_cxx_source_compiles("
  #include <vector>
  #include <future>
  int main() { std::vector<std::future<int>> v; }" HAVE_STD_FUTURE)