test: don't run jobs in parallel

Since we do not have a lot of tests, we can afford to run them one after
the other (no parallelism). This makes it easier to read the output
because output of different tests does not interleave.

Author: giomba

src/main_test.c

@@ -10,6 +10,7 @@ int main(int argc, char *argv[]) {
     criterion_options.full_stats = true;
     criterion_options.timeout = 1;
     criterion_options.logging_threshold = CRITERION_INFO;
+    criterion_options.jobs = 1;
 
     struct criterion_test_set *set = criterion_initialize();
     if (criterion_handle_args(argc, argv, true))