When a prereq.sh file determines that a test can't run because the feature

to be tested was not configured in at build time, it can now return 255,
and run.sh will print "R:SKIPPED" instead of "R:UNTESTED".  Robie will be
able to flag this as green rather than yellow.

bin/tests/system/dlzexternal/prereq.sh

@@ -5,7 +5,7 @@ TOP=${SYSTEMTESTTOP:=.}/../../../..
 # enable the dlzexternal test only if it builds and dlz-dlopen was enabled
 $TOP/bin/named/named -V | grep with.dlz.dlopen | grep -v with.dlz.dlopen=no > /dev/null || {
     echo "I:not built with --with-dlz-dlopen=yes - skipping dlzexternal test"
-    exit 1
+    exit 255
 }
 
 cd ../../../../contrib/dlz/example && make all > /dev/null || {