fix default build when crypt() is unavailable if the system doesn't support crypt.h/crypt, then ENABLE_SVR_PASSWORD_AUTH cannot work. rather than default this to on all the time, do so only when support for the header is found.

#!/bin/sh
exec 2>&1
exec dropbear -d ./dropbear_dss_host_key -r ./dropbear_rsa_host_key -F -E -p 22