README incorrectly suggests build sources spark-env.sh
README incorrectly suggests build sources spark-env.sh

This is misleading because the build doesn't source that file. IMO
it's better to force people to specify build environment variables
on the command line always, like we do in every example.

stanzhai/spark,ueshin/apache-spark,stanzhai/spark,jiangxb1987/spark,andrewor14/iolap,dotunolafunmiloye/spark,mahak/spark,shuangshuangwang/spark,wangyum/spark,tengpeng/spark,spark-test/spark,markhamstra/spark,stanzhai/spark,jianran/spark,markhamstra/spark,sureshthalamati/spark,ericvandenbergfb/spark,ajaysaini725/spark,goldmedal/spark,pgandhi999/spark,big-pegasus/spark,lxsmnv/spark,dbtsai/spark,lxsmnv/spark,aray/spark,lvdongr/spark,facaiy/spark,mike0sv/spark,shaneknapp/spark,hvanhovell/spark,gioenn/xSpark,eyalfa/spark,icexelloss/spark,srowen/spark,vinodkc/spark,goldmedal/spark,sureshthalamati/spark,JoshRosen/spark,lxsmnv/spark,alunarbeach/spark,janewangfb/spark,szhem/spark,pronix/spark,rednaxelafx/apache-spark,map222/spark,loneknightpy/spark,apache-spark-on-k8s/spark,yanboliang/spark,dongjoon-hyun/spark,adrian-ionescu/apache-spark,setjet/spark,patrick-nicholson/spark,dongjoon-hyun/spark,jlopezmalla/spark,patrick-nicholson/spark,szhem/spark,zuotingbing/spark,hvanhovell/spark,rikima/spark,witgo/spark,zuotingbing/spark,byakuinss/spark,chuckchen/spark,rednaxelafx/apache-spark,poffuomo/spark,wangyum/spark,UndeadBaneGitHub/spark,UndeadBaneGitHub/spark,icexelloss/spark,matthewfranglen/spark,dhruve/spark,dbtsai/spark,nilsgrabbert/spark,icexelloss/spark,BryanCutler/spark,akopich/spark,Aegeaner/spark,mzl9039/spark,bdrillard/spark,esi-mineset/spark,jkbradley/spark,ibm-research-ireland/sparkoscope,shubhamchopra/spark,michalsenkyr/spark,nilsgrabbert/spark,wangyum/spark,publicRoman/spark,ConeyLiu/spark,holdenk/spark,ajaysaini725/spark,tejasapatil/spark,xuanyuanking/spark,aosagie/spark,vinodkc/spark,sahilTakiar/spark,Panos-Bletsos/spark-cost-model-optimizer,stanzhai/spark,guoxiaolongzte/spark,eyalfa/spark,BryanCutler/spark,tengpeng/spark,caneGuy/spark,JoshRosen/spark,witgo/spark,mahak/spark,huang1900/spark,cloudera/spark,szhem/spark,WindCanDie/spark,sachintyagi22/spark,milliman/spark,akopich/spark,adrian-ionescu/apache-spark,bOOm-X/spark,kissmetrics/spark,darionyaphet/spark,zzcclp/spark,kevinyu98/spark,bravo-zhang/spark,nchammas/spark,witgo/spark,highfei2011/spark,zhouyejoe/spark,nlalevee/spark,JoshRosen/spark,pronix/spark,mzl9039/spark,sureshthalamati/spark,jianran/spark,bOOm-X/spark,BryanCutler/spark,techaddict/spark,jlopezmalla/spark,Aegeaner/spark,pgandhi999/spark,wzhfy/spark,caneGuy/spark,yanboliang/spark,cloud-fan/spark,skonto/spark,ahnqirage/spark,metamx/spark,bOOm-X/spark,michalsenkyr/spark,stanzhai/spark,someorz/spark,spark-test/spark,alunarbeach/spark,metamx/spark,pronix/spark,liyichao/spark,techaddict/spark,huang1900/spark,eyalfa/spark,MLnick/spark,actuaryzhang/spark,facaiy/spark,zuotingbing/spark,metamx/spark,sahilTakiar/spark,maropu/spark,chuckchen/spark,vinodkc/spark,nlalevee/spark,ueshin/apache-spark,kiszk/spark,milliman/spark,hvanhovell/spark,BryanCutler/spark,ddna1021/spark,caneGuy/spark,sureshthalamati/spark,skonto/spark,facaiy/spark,gengliangwang/spark,publicRoman/spark,zhouyejoe/spark,shaneknapp/spark,ron8hu/spark,yanboliang/spark,holdenk/spark,kevinyu98/spark,SnappyDataInc/spark,gioenn/xSpark,ioana-delaney/spark,saturday-shi/spark,bOOm-X/spark,dhruve/spark,ddna1021/spark,mahak/spark,ptkool/spark,tengpeng/spark,MLnick/spark,rekhajoshm/spark,jianran/spark,JoshRosen/spark,shaneknapp/spark,hhbyyh/spark,xuanyuanking/spark,LantaoJin/spark,lvdongr/spark,mkolod/incubator-spark,darionyaphet/spark,wangyum/spark,metamx/spark,debugger87/spark,chuckchen/spark,markhamstra/spark,skonto/spark,byakuinss/spark,liutang123/spark,minixalpha/spark,aokolnychyi/spark,aokolnychyi/spark,cin/spark,hhbyyh/spark,rekhajoshm/spark,1haodian/spark,zero323/spark,srowen/spark,someorz/spark,byakuinss/spark,map222/spark,kiszk/spark,saltstar/spark,kissmetrics/spark,andrewor14/iolap,jlopezmalla/spark,wzhfy/spark,maropu/spark,ajaysaini725/spark,szhem/spark,sureshthalamati/spark,ericvandenbergfb/spark,shubhamchopra/spark,SHASHANKB/spark,liyichao/spark,jkbradley/spark,dongjoon-hyun/spark,skonto/spark,sachintyagi22/spark,bdrillard/spark,jkbradley/spark,rikima/spark,kiszk/spark,yanboliang/spark,minixalpha/spark,eyalfa/spark,bdrillard/spark,UndeadBaneGitHub/spark,kimoonkim/spark,markhamstra/spark,liyichao/spark,huang1900/spark,xflin/spark,rednaxelafx/apache-spark,jrshust/spark,andrewor14/spark,hhbyyh/spark,ConeyLiu/spark,JoshRosen/spark,witgo/spark,kissmetrics/spark,mike0sv/spark,huang1900/spark,esi-mineset/spark,liutang123/spark,lvdongr/spark,cloudera/spark,pgandhi999/spark,milliman/spark,Aegeaner/spark,jiangxb1987/spark,nlalevee/spark,setjet/spark,markhamstra/spark,aray/spark,stanzhai/spark,SnappyDataInc/spark,BryanCutler/spark,darionyaphet/spark,tengpeng/spark,ibm-research-ireland/sparkoscope,vinodkc/spark,goldmedal/spark,actuaryzhang/spark,caneGuy/spark,gengliangwang/spark,milliman/spark,michalsenkyr/spark,akopich/spark,zhouyejoe/spark,JerryLead/spark,vinodkc/spark,setjet/spark,poffuomo/spark,markhamstra/spark,kissmetrics/spark,highfei2011/spark,patrick-nicholson/spark,sachintyagi22/spark,ptkool/spark,brad-kaiser/spark,apache/spark,lvdongr/spa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