ruby: explicitly disable SSP support

ruby: explicitly disable SSP support

The SSP support checks of the Ruby configure script do not do a full
link, and therefore don't properly detect if SSP support is fully
functional or not, which causes some build failures if the compiler
supports -fstack-protector but the C library does not provide the SSP
implementation.

To avoid this, we explicitly tell ruby if SSP support is available or
not.

Fixes:

  http://autobuild.buildroot.net/results/001/00154b0142f51c197d5d53ae36f7adc4f8250d9d/

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>