glsl/tests/warnings-test: error if zero tests were executed

We don't want to lie ourselves that 'everything is fine' when no tests
were found/ran.

Signed-off-by: Emil Velikov <emil.velikov@collabora.com>
Acked-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Eric Engestrom <eric.engestrom@imgtec.com>

src/compiler/glsl/tests/warnings-test.sh

@@ -42,6 +42,11 @@ for test in $srcdir/$tests_relative_dir/*.vert; do
     fi
 done
 
+if [ $total -eq 0 ]; then
+    echo "Could not find any tests."
+    exit 1
+fi
+
 echo ""
 echo "$pass/$total tests returned correct results"
 echo ""