workqueue: use BUILD_BUG_ON() for compile time test instead of WARN_ON()

Any runtime WARN_ON() has to be fixed, and BUILD_BUG_ON() can
help you nitice it earlier.
Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

kernel/workqueue.c

@@ -5917,7 +5917,7 @@ void __init workqueue_init_early(void)
 	int hk_flags = HK_FLAG_DOMAIN | HK_FLAG_WQ;
 	int i, cpu;
 
-	WARN_ON(__alignof__(struct pool_workqueue) < __alignof__(long long));
+	BUILD_BUG_ON(__alignof__(struct pool_workqueue) < __alignof__(long long));
 
 	BUG_ON(!alloc_cpumask_var(&wq_unbound_cpumask, GFP_KERNEL));
 	cpumask_copy(wq_unbound_cpumask, housekeeping_cpumask(hk_flags));