Add the check of Android API level which must not be lower than 21.
Add the check of Android API level which must not be lower than 21.

PaddlePaddle/Paddle,tensor-tang/Paddle,luotao1/Paddle,lispc/Paddle,Canpio/Paddle,cxysteven/Paddle,pkuyym/Paddle,pengli09/Paddle,baidu/Paddle,chengduoZH/Paddle,pengli09/Paddle,jacquesqiao/Paddle,jacquesqiao/Paddle,pkuyym/Paddle,lcy-seso/Paddle,pengli09/Paddle,lcy-seso/Paddle,pengli09/Paddle,chengduoZH/Paddle,QiJune/Paddle,Canpio/Paddle,emailweixu/Paddle,yu239/Paddle,putcn/Paddle,pengli09/Paddle,cxysteven/Paddle,chengduoZH/Paddle,yu239/Paddle,yu239/Paddle,reyoung/Paddle,PaddlePaddle/Paddle,QiJune/Paddle,tensor-tang/Paddle,pkuyym/Paddle,lispc/Paddle,hedaoyuan/Paddle,chengduoZH/Paddle,yu239/Paddle,hedaoyuan/Paddle,cxysteven/Paddle,reyoung/Paddle,emailweixu/Paddle,emailweixu/Paddle,lispc/Paddle,Canpio/Paddle,QiJune/Paddle,tensor-tang/Paddle,pengli09/Paddle,jacquesqiao/Paddle,luotao1/Paddle,putcn/Paddle,cxysteven/Paddle,cxysteven/Paddle,hedaoyuan/Paddle,putcn/Paddle,Canpio/Paddle,hedaoyuan/Paddle,putcn/Paddle,pkuyym/Paddle,baidu/Paddle,jacquesqiao/Paddle,QiJune/Paddle,luotao1/Paddle,baidu/Paddle,lispc/Paddle,emailweixu/Paddle,lcy-seso/Paddle,reyoung/Paddle,emailweixu/Paddle,lcy-seso/Paddle,lispc/Paddle,Canpio/Paddle,chengduoZH/Paddle,hedaoyuan/Paddle,Canpio/Paddle,reyoung/Paddle,lispc/Paddle,hedaoyuan/Paddle,PaddlePaddle/Paddle,reyoung/Paddle,hedaoyuan/Paddle,yu239/Paddle,luotao1/Paddle,cxysteven/Paddle,baidu/Paddle,PaddlePaddle/Paddle,putcn/Paddle,PaddlePaddle/Paddle,lispc/Paddle,pengli09/Paddle,cxysteven/Paddle,pengli09/Paddle,emailweixu/Paddle,Canpio/Paddle,jacquesqiao/Paddle,PaddlePaddle/Paddle,tensor-tang/Paddle,jacquesqiao/Paddle,lcy-seso/Paddle,luotao1/Paddle,putcn/Paddle,baidu/Paddle,QiJune/Paddle,lispc/Paddle,emailweixu/Paddle,lcy-seso/Paddle,PaddlePaddle/Paddle,reyoung/Paddle,yu239/Paddle,luotao1/Paddle,tensor-tang/Paddle,luotao1/Paddle,pkuyym/Paddle,yu239/Paddle,Canpio/Paddle,yu239/Paddle,pkuyym/Paddle,hedaoyuan/Paddle,QiJune/Paddle