ntp: fix build without SSP support

ntp: fix build without SSP support

In version 4.2.8p11 ntp changed its configure script build hardening
parameter to '--with-hardenfile'. Update the parameter name to avoid
-fstack-protector-all when the toolchain does not support this option.

Fixes:
http://autobuild.buildroot.net/results/60e/60e8b9864932f2cabc7deb43234abe168bd113c5/
http://autobuild.buildroot.net/results/592/592db6836817bb078a2f1146d2ce6241bf7997a3/
http://autobuild.buildroot.net/results/b07/b070fbc66a928888df8d2561dad3632778d55e0d/

Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>