libice 1.0.9 added automatic detection of arc4random(), which is in libbsd on
Linux. As this is automatic and leads to failing builds when ssstate is reused,
seed the autoconf cache as relevant to implement a PACKAGECONFIG for the
functionality.
Default to not using arc4random() as the fallback has been in use for many
years, but people interested in security may wish to turn this on to increase
the security of the X authentication cookies.
Signed-off-by: Ross Burton <ross.burton@intel.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
