cmake CPROF_HAVE_TIMESPEC_GET examples

fluent/fluent-bit lib/cprofiles/CMakeLists.txt :66

check_c_source_compiles("
  #include <time.h>
  int main() {
     struct tm tm;
     return timespec_get(&tm, TIME_UTC);
  }" CPROF_HAVE_TIMESPEC_GET)