Add CONFIG_POSIX_MQUEUE to check-config.sh

Signed-off-by: Andrew "Tianon" Page <admwiggin@gmail.com>

contrib/check-config.sh

@@ -138,6 +138,9 @@ flags=(
 	NF_NAT_IPV4 IP_NF_FILTER IP_NF_TARGET_MASQUERADE
 	NETFILTER_XT_MATCH_{ADDRTYPE,CONNTRACK}
 	NF_NAT NF_NAT_NEEDED
+
+	# required for bind-mounting /dev/mqueue into containers
+	POSIX_MQUEUE
 )
 check_flags "${flags[@]}"
 echo