Enable forkjoin parallel workers only if we have hwloc, otherwise we don't have code to bind/unbind threads.

src/core/workers.c

@@ -168,7 +168,11 @@ int starpu_combined_worker_can_execute_task(unsigned workerid, struct starpu_tas
 	}
 	else
 	{
-		if ((cl->type == STARPU_SPMD) || (cl->type == STARPU_FORKJOIN))
+		if ((cl->type == STARPU_SPMD)
+#ifdef STARPU_HAVE_HWLOC
+				|| (cl->type == STARPU_FORKJOIN)
+#endif
+				)
 		{
 			/* TODO we should add other types of constraints */