cmake EXECINFO_LIBC_HAS_BACKTRACE examples

fcitx/fcitx5 cmake/FindExecinfo.cmake :12 

check_function_exists(backtrace EXECINFO_LIBC_HAS_BACKTRACE)

fcitx/fcitx5 cmake/FindExecinfo.cmake :33 

mark_as_advanced(EXECINFO_INCLUDE_DIR EXECINFO_LIBRARY EXECINFO_LIBC_HAS_BACKTRACE)