testlib selftest: Actually report failures as non-zero exit code

Palm, meet face.

Change-Id: I01cd4088c8f43f7fe66398c27f5d8333468620ad
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>

tests/auto/testlib/selftests/tst_selftests.cpp

@@ -1243,6 +1243,8 @@ int main(int argc, char **argv)
         qDebug() << "Test outputs left in" << qUtf8Printable(testOutputDir.path());
         testOutputDir.setAutoRemove(false);
     }
+
+    return result;
 #endif
 }