cmake HAVE_EXECINFO_BACKTRACE examples

google/glog CMakeLists.txt :155 

check_cxx_symbol_exists (backtrace execinfo.h HAVE_EXECINFO_BACKTRACE)

google/glog CMakeLists.txt :243 

endif (HAVE_EXECINFO_BACKTRACE AND HAVE_EXECINFO_BACKTRACE_SYMBOLS)