some targets do not define the _REDIR_TIME64 macro resulting in a
build error regression since ddfe5678a4
fix by checking if the macro is defined
[1] https://github.com/openwrt/openwrt/issues/12587Fixes: #12587
Fixes: ddfe5678a4 ("fortify-headers: fix inconsistent time_t version of ppoll")
Signed-off-by: Georgi Valkov <gvalkov@gmail.com>