tsiggss test needed a prereq.sh file. (Committing without review because

the script is simple, no one is available, and I want to shut robie up.)

bin/tests/system/tsiggss/prereq.sh

@@ -0,0 +1,11 @@
+#!/bin/sh
+
+TOP=${SYSTEMTESTTOP:=.}/../../../..
+
+# enable the tsiggss test only if gssapi was enabled
+$TOP/bin/named/named -V | grep with.gssapi | grep -v with-gssapi=no > /dev/null || {
+    echo "I:BIND9 was not built with --with-gssapi"
+    exit 1
+}
+
+exit 0