tests: add status about missing kernel support

Some tests might fail due to a lack of kernel support, such as a
missing driver which have to to be involved for running such
tests. Introduce the EXIT_NO_SUPPORT code for this case, to be
distinguished by the test runner from a functional failure.

tests/helpers.h

@@ -11,6 +11,8 @@
 #include <errno.h>
 #include <pthread.h>
 
+#define EXIT_NO_SUPPORT  42
+
 #define __stringify_1(x...)	#x
 #define __stringify(x...)	__stringify_1(x)
 

utils/test.evl

@@ -73,8 +73,12 @@ for t in $test_list; do
     test \! -x $t && echo "$(basename $t): no such test" && exit 2
     $t && echo "$(basename $t): OK" && continue
     c=$?
-    echo "** $(basename $t): BROKEN"
-    test x$keep_going = xfalse && exit $c
+    if test $c = 42; then
+	echo "$(basename $t): no kernel support"
+    else
+	echo "** $(basename $t): BROKEN"
+	test x$keep_going = xfalse && exit $c
+    fi
 done
 
 exit 0