Only enable SSE2 flags when detected (#3854)
Only enable SSE2 flags when detected (#3854)

SSE2 flags were always being enabled, making the feature test
irrelevant. This should make it so SSE2 is enabled when detected.
thirdwing/mxnet,ykim362/mxnet,crazy-cat/incubator-mxnet,Guneet-Dhillon/mxnet,xcgoner/dist-mxnet,mbaijal/incubator-mxnet,apache/incubator-mxnet,solin319/incubator-mxnet,antoan2/incubator-mxnet,zhreshold/mxnet,wangyum/mxnet,leezu/mxnet,yuruofeifei/mxnet,kevinthesun/mxnet,jermainewang/mxnet,precedenceguo/mxnet,fullfanta/mxnet,LinkHS/incubator-mxnet,tlby/mxnet,lxn2/mxnet,jiajiechen/mxnet,reminisce/mxnet,CodingCat/mxnet,apaleyes/mxnet,solin319/incubator-mxnet,madjam/mxnet,indhub/mxnet,hpi-xnor/BMXNet,ZihengJiang/mxnet,dmlc/mxnet,smolix/incubator-mxnet,yajiedesign/mxnet,Guneet-Dhillon/mxnet,zhreshold/mxnet,crazy-cat/incubator-mxnet,ZihengJiang/mxnet,gautamkmr/incubator-mxnet,ptrendx/mxnet,indhub/mxnet,saurabh3949/mxnet,weleen/mxnet,DickJC123/mxnet,jiajiechen/mxnet,kevinthesun/mxnet,solin319/incubator-mxnet,DickJC123/mxnet,rishita/mxnet,kevinthesun/mxnet,weleen/mxnet,LinkHS/incubator-mxnet,tlby/mxnet,fullfanta/mxnet,vikingMei/mxnet,pluskid/mxnet,sergeykolychev/mxnet,mbaijal/incubator-mxnet,Ldpe2G/mxnet,eric-haibin-lin/mxnet,madjam/mxnet,apache/incubator-mxnet,xcgoner/dist-mxnet,rahul003/mxnet,gautamkmr/incubator-mxnet,mbaijal/incubator-mxnet,yuruofeifei/mxnet,jamesliu/mxnet,sxjscience/mxnet,TuSimple/mxnet,jiajiechen/mxnet,arikpoz/mxnet,smolix/incubator-mxnet,danithaca/mxnet,TuSimple/mxnet,TuSimple/mxnet,yajiedesign/mxnet,navrasio/mxnet,rishita/mxnet,jennyzhang0215/incubator-mxnet,hpi-xnor/BMXNet,gautamkmr/incubator-mxnet,zhreshold/mxnet,kkk669/mxnet,Guneet-Dhillon/mxnet,leezu/mxnet,apaleyes/mxnet,hesseltuinhof/mxnet,ykim362/mxnet,yajiedesign/mxnet,reminisce/mxnet,nicklhy/mxnet,szha/mxnet,formath/mxnet,arikpoz/mxnet,eric-haibin-lin/mxnet,piiswrong/mxnet,arikpoz/mxnet,jiajiechen/mxnet,ptrendx/mxnet,ykim362/mxnet,xcgoner/dist-mxnet,sxjscience/mxnet,hotpxl/mxnet,jamesliu/mxnet,TuSimple/mxnet,ZihengJiang/mxnet,thirdwing/mxnet,saurabh3949/mxnet,Guneet-Dhillon/mxnet,kevinthesun/mxnet,Prasad9/incubator-mxnet,mbaijal/incubator-mxnet,apaleyes/mxnet,Northrend/mxnet,arank/mxnet,lxn2/mxnet,jermainewang/mxnet,danithaca/mxnet,Ldpe2G/mxnet,madjam/mxnet,tornadomeet/mxnet,thirdwing/mxnet,eric-haibin-lin/mxnet,gautamkmr/incubator-mxnet,dmlc/mxnet,lxn2/mxnet,sxjscience/mxnet,apache/incubator-mxnet,larroy/mxnet,CodingCat/mxnet,rahul003/mxnet,pluskid/mxnet,DR08/mxnet,Mega-DatA-Lab/mxnet,reminisce/mxnet,Prasad9/incubator-mxnet,zhreshold/mxnet,hpi-xnor/BMXNet,gautamkmr/incubator-mxnet,larroy/mxnet,weleen/mxnet,weleen/mxnet,precedenceguo/mxnet,jamesliu/mxnet,arikpoz/mxnet,jermainewang/mxnet,weleen/mxnet,LinkHS/incubator-mxnet,piiswrong/mxnet,crazy-cat/incubator-mxnet,leezu/mxnet,madjam/mxnet,Ldpe2G/mxnet,coder-james/mxnet,ForkedReposBak/mxnet,leezu/mxnet,antoan2/incubator-mxnet,Northrend/mxnet,pluskid/mxnet,ptrendx/mxnet,rahul003/mxnet,hotpxl/mxnet,hotpxl/mxnet,ShownX/incubator-mxnet,thirdwing/mxnet,apaleyes/mxnet,arikpoz/mxnet,rishita/mxnet,Mega-DatA-Lab/mxnet,sergeykolychev/mxnet,crazy-cat/incubator-mxnet,solin319/incubator-mxnet,ForkedReposBak/mxnet,yuruofeifei/mxnet,Prasad9/incubator-mxnet,sxjscience/mxnet,hpi-xnor/BMXNet,yajiedesign/mxnet,crazy-cat/incubator-mxnet,yajiedesign/mxnet,CodingCat/mxnet,kkk669/mxnet,zhreshold/mxnet,rahul003/mxnet,DR08/mxnet,jennyzhang0215/incubator-mxnet,yuruofeifei/mxnet,navrasio/mxnet,wangyum/mxnet,Mega-DatA-Lab/mxnet,Prasad9/incubator-mxnet,jennyzhang0215/incubator-mxnet,smolix/incubator-mxnet,Northrend/mxnet,jamesliu/mxnet,solin319/incubator-mxnet,TuSimple/mxnet,leezu/mxnet,tornadomeet/mxnet,mbaijal/incubator-mxnet,Guneet-Dhillon/mxnet,gautamkmr/incubator-mxnet,dmlc/mxnet,wangyum/mxnet,nicklhy/mxnet,antoan2/incubator-mxnet,Guneet-Dhillon/mxnet,arank/mxnet,jamesliu/mxnet,stefanhenneking/mxnet,TuSimple/mxnet,antoan2/incubator-mxnet,sxjscience/mxnet,saurabh3949/mxnet,saurabh3949/mxnet,LinkHS/incubator-mxnet,szha/mxnet,hpi-xnor/BMXNet,hotpxl/mxnet,ForkedReposBak/mxnet,LinkHS/incubator-mxnet,danithaca/mxnet,Guneet-Dhillon/mxnet,larroy/mxnet,likelyzhao/mxnet,Ldpe2G/mxnet,rishita/mxnet,leezu/mxnet,yajiedesign/mxnet,ZihengJiang/mxnet,precedenceguo/mxnet,ZihengJiang/mxnet,formath/mxnet,madjam/mxnet,gautamkmr/incubator-mxnet,piiswrong/mxnet,mbaijal/incubator-mxnet,indhub/mxnet,mbaijal/incubator-mxnet,wangyum/mxnet,luoyetx/mxnet,solin319/incubator-mxnet,navrasio/mxnet,LinkHS/incubator-mxnet,yajiedesign/mxnet,kevinthesun/mxnet,EvanzzzZ/mxnet,ShownX/incubator-mxnet,vikingMei/mxnet,dmlc/mxnet,formath/mxnet,luoyetx/mxnet,likelyzhao/mxnet,jennyzhang0215/incubator-mxnet,hpi-xnor/BMXNet,nicklhy/mxnet,gautamkmr/incubator-mxnet,smolix/incubator-mxnet,arikpoz/mxnet,piiswrong/mxnet,yajiedesign/mxnet,hesseltuinhof/mxnet,EvanzzzZ/mxnet,navrasio/mxnet,stefanhenneking/mxnet,nicklhy/mxnet,likelyzhao/mxnet,indhub/mxnet,CodingCat/mxnet,Ldpe2G/mxnet,rahul003/mxnet,formath/mxnet,rahul003/mxnet,EvanzzzZ/mxnet,hotpxl/mxnet,wangyum/mxnet,Prasad9/incubator-mxnet,lxn2/mxnet,precedenceguo/mxnet,navrasio/mxnet,jamesliu/mxnet,zhreshold/mxnet,CodingCat/mxnet,jermainewang/mxnet,dmlc/mxnet,eric-haibin-lin/mxnet,navrasio/mxnet,thirdwing/mxnet,Northrend/mxnet,jamesliu/mxnet,Prasad9/incubator-mxnet,saurabh3949/mxnet,hesseltuinhof/mxnet,gautamkmr/incubator-mxnet,stefanhenneking/mxnet,ShownX/incubator-mxnet,hesseltuinhof/mxnet,rishita/mxnet,weleen/mxnet,hpi-xnor/BMXNet,arank/mxnet,CodingCat/mxnet,pluskid/mxnet,rishita/mxnet,Prasad9/incubator-mxnet,ptrendx/mxnet,stefanhenneking/mxnet,yuruofeifei/mxnet,Prasad9/incubator-mxnet,luoyetx/mxnet,reminisce/mxnet,arank/mxnet,larroy/mxnet,crazy-cat/incubator-mxnet,saurabh3949/mxnet,jennyzhang0215/incubator-mxnet,TuSimple/mxnet,fullfanta/mxnet,EvanzzzZ/mxnet,coder-james/mxnet,szha/mxnet,DickJC123/mxnet,jennyzhang0215/incubator-mxnet,DR08/mxnet,dmlc/mxnet,coder-james/mxnet,luoyetx/mxnet,ykim362/mxnet,madjam/mxnet,zhreshold/mxnet,sxjscience/mxnet,danithaca/mxnet,ShownX/incubator-mxnet,eric-haibin-lin/mxnet,luoyetx/mxnet,reminisce/mxnet,TuSimple/mxnet,rishita/mxnet,Northrend/mxnet,danithaca/mxnet,rahul003/mxnet,Northrend/mxnet,zhreshold/mxnet,coder-james/mxnet,wangyum/mxnet,nicklhy/mxnet,thirdwing/mxnet,pluskid/mxnet,ShownX/incubator-mxnet,hesseltuinhof/mxnet,indhub/mxnet,ptrendx/mxnet,saurabh3949/mxnet,ForkedReposBak/mxnet,ShownX/incubator-mxnet,ZihengJiang/mxnet,xcgoner/dist-mxnet,sergeykolychev/mxnet,ptrendx/mxnet,Ldpe2G/mxnet,sergeykolychev/mxnet,LinkHS/incubator-mxnet,lxn2/mxnet,reminisce/mxnet,EvanzzzZ/mxnet,larroy/mxnet,piiswrong/mxnet,eric-haibin-lin/mxnet,pluskid/mxnet,DR08/mxnet,Northrend/mxnet,kkk669/mxnet,EvanzzzZ/mxnet,sergeykolychev/mxnet,indhub/mxnet,tornadomeet/mxnet,eric-haibin-lin/mxnet,ZihengJiang/mxnet,vikingMei/mxnet,formath/mxnet,ForkedReposBak/mxnet,jiajiechen/mxnet,larroy/mxnet,szha/mxnet,sxjscience/mxnet,nicklhy/mxnet,xcgoner/dist-mxnet,dmlc/mxnet,ForkedReposBak/mxnet,jermainewang/mxnet,luoyetx/mxnet,jermainewang/mxnet,stefanhenneking/mxnet,szha/mxnet,jennyzhang0215/incubator-mxnet,ykim362/mxnet,likelyzhao/mxnet,precedenceguo/mxnet,jermainewang/mxnet,solin319/incubator-mxnet,vikingMei/mxnet,tornadomeet/mxnet,yajiedesign/mxnet,CodingCat/mxnet,thirdwing/mxnet,kkk669/mxnet,arank/mxnet,hesseltuinhof/mxnet,tornadomeet/mxnet,ShownX/incubator-mxnet,indhub/mxnet,precedenceguo/mxnet,Ldpe2G/mxnet,kkk669/mxnet,tlby/mxnet,tornadomeet/mxnet,smolix/incubator-mxnet,rahul003/mxnet,hotpxl/mxnet,likelyzhao/mxnet,danithaca/mxnet,leezu/mxnet,leezu/mxnet,formath/mxnet,Mega-DatA-Lab/mxnet,kkk669/mxnet,madjam/mxnet,precedenceguo/mxnet,likelyzhao/mxnet,tlby/mxnet,hpi-xnor/BMXNet,madjam/mxnet,xcgoner/dist-mxnet,jiajiechen/mxnet,weleen/mxnet,solin319/incubator-mxnet,arikpoz/mxnet,Mega-DatA-Lab/mxnet,DR08/mxnet,ptrendx/mxnet,reminisce/mxnet,ykim362/mxnet,lxn2/mxnet,tlby/mxnet,szha/mxnet,rishita/mxnet,CodingCat/mxnet,precedenceguo/mxnet,ForkedReposBak/mxnet,tornadomeet/mxnet,sergeykolychev/mxnet,smolix/incubator-mxnet,EvanzzzZ/mxnet,kkk669/mxnet,antoan2/incubator-mxnet,formath/mxnet,DR08/mxnet,sxjscience/mxnet,eric-haibin-lin/mxnet,Mega-DatA-Lab/mxnet,xcgoner/dist-mxnet,tlby/mxnet,Ldpe2G/mxnet,xcgoner/dist-mxnet,fullfanta/mxnet,danithaca/mxnet,danithaca/mxnet,antoan2/incubator-mxnet,tornadomeet/mxnet,stefanhenneking/mxnet,indhub/mxnet,wangyum/mxnet,arank/mxnet,Mega-DatA-Lab/mxnet,smolix/incubator-mxnet,ptrendx/mxnet,antoan2/incubator-mxnet,jamesliu/mxnet,arank/mxnet,kevinthesun/mxnet,TuSimple/mxnet,formath/mxnet,likelyzhao/mxnet,crazy-cat/incubator-mxnet,szha/mxnet,likelyzhao/mxnet,likelyzhao/mxnet,piiswrong/mxnet,Northrend/mxnet,piiswrong/mxnet,Prasad9/incubator-mxnet,madjam/mxnet,apaleyes/mxnet,lxn2/mxnet,coder-james/mxnet,luoyetx/mxnet,DR08/mxnet,Mega-DatA-Lab/mxnet,thirdwing/mxnet,zhreshold/mxnet,precedenceguo/mxnet,larroy/mxnet,arank/mxnet,hotpxl/mxnet,apache/incubator-mxnet,kevinthesun/mxnet,luoyetx/mxnet,kevinthesun/mxnet,leezu/mxnet,hesseltuinhof/mxnet,ykim362/mxnet,crazy-cat/incubator-mxnet,saurabh3949/mxnet,vikingMei/mxnet,mbaijal/incubator-mxnet,stefanhenneking/mxnet,reminisce/mxnet,tlby/mxnet,coder-james/mxnet,rahul003/mxnet,weleen/mxnet,yuruofeifei/mxnet,nicklhy/mxnet,szha/mxnet,hotpxl/mxnet,reminisce/mxnet,antoan2/incubator-mxnet,tlby/mxnet,ZihengJiang/mxnet,DR08/mxnet,vikingMei/mxnet,ForkedReposBak/mxnet,crazy-cat/incubator-mxnet,rishita/mxnet,LinkHS/incubator-mxnet,lxn2/mxnet,hotpxl/mxnet,apaleyes/mxnet,piiswrong/mxnet,larroy/mxnet,hesseltuinhof/mxnet,szha/mxnet,Guneet-Dhillon/mxnet,coder-james/mxnet,kevinthesun/mxnet,thirdwing/mxnet,ShownX/incubator-mxnet,coder-james/mxnet,smolix/incubator-mxnet,luoyetx/mxnet,ptrendx/mxnet,nicklhy/mxnet,sergeykolychev/mxnet,pluskid/mxnet,EvanzzzZ/mxnet,Northrend/mxnet,smolix/incubator-mxnet,nicklhy/mxnet,indhub/mxnet,fullfanta/mxnet,lxn2/mxnet,reminisce/mxnet,dmlc/mxnet,jiajiechen/mxnet,EvanzzzZ/mxnet,Ldpe2G/mxnet,fullfanta/mxnet,antoan2/incubator-mxnet,LinkHS/incubator-mxnet,pluskid/mxnet,arikpoz/mxnet,Mega-DatA-Lab/mxnet,ykim362/mxnet,kkk669/mxnet,dmlc/mxnet,saurabh3949/mxnet,apaleyes/mxnet,navrasio/mxnet,yuruofeifei/mxnet,formath/mxnet,ForkedReposBak/mxnet,jamesliu/mxnet,larroy/mxnet,coder-james/mxnet,tlby/mxnet,stefanhenneking/mxnet,apaleyes/mxnet,fullfanta/mxnet,TuSimple/mxnet,ykim362/mxnet,wangyum/mxnet,pluskid/mxnet,stefanhenneking/mxnet,fullfanta/mxnet,wangyum/mxnet,navrasio/mxnet,sergeykolychev/mxnet,DR08/mxnet,weleen/mxnet,hpi-xnor/BMXNet,jiajiechen/mxnet,mbaijal/incubator-mxnet,arank/mxnet,ShownX/incubator-mxnet,jermainewang/mxnet,piiswrong/mxnet,DickJC123/mxnet,apaleyes/mxnet,fullfanta/mxnet,yuruofeifei/mxnet,vikingMei/mxnet,Guneet-Dhillon/mxnet,yuruofeifei/mxnet,kkk669/mxnet,vikingMei/mxnet,solin319/incubator-mxnet,jennyzhang0215/incubator-mxnet,CodingCat/mxnet,jennyzhang0215/incubator-mxnet,sxjscience/mxnet,vikingMei/mxnet,sergeykolychev/mxnet,tlby/mxnet,ZihengJiang/mxnet,ptrendx/mxnet,danithaca/mxnet,tornadomeet/mxnet,xcgoner/dist-mxnet,navrasio/mxnet,jiajiechen/mxnet,eric-haibin-lin/mxnet,hesseltuinhof/mxnet,arikpoz/mxnet,jermainewang/mxnet