Default to NODE_ENV=production during runtime
Default to NODE_ENV=production during runtime

This was added in 459ebb67baff09c62fe10d24d9b530915b1da722 and
mistakenly removed in 043067eb8cc30cfd05115e105c0678c859c12c28.

mrc535s/wkhtmltopdfbp,cloudfoundry/nodejs-buildpack,karthikeyabhaghavatula/nodejs_buildpack,heroku/heroku-buildpack-nodejs,pkumar-appd/nodejs-buildpack,Scalingo/nodejs-buildpack,ks2software/nodejs-buildpack,kauffecup/nodejs-buildpack,Grahahax/nodejs-buildpack,caiorogerio/heroku-buildpack-grunt,ks2software/nodejs-buildpack,ks2software/nodejs-buildpack,fcruxen/heroku-buildpack-nodejs,pkumar-appd/nodejs-buildpack,cheeyeo/heroku-buildpack-nodejs,sailrish/heroku-buildpack-coffee,roder/nodejs-buildpack,kauffecup/nodejs-buildpack,The18thWarrior/ethereum-buildpack,TJM/heroku-buildpack-nodejs,carouselapps/heroku-buildpack-nodejs,karthikeyabhaghavatula/nodejs_buildpack,Grahahax/nodejs-buildpack,kauffecup/nodejs-buildpack,shuber/heroku-buildpack-nodejs,heroku/heroku-buildpack-nodejs,mrc535s/wkhtmltopdfbp,NSWIDER/nodejs-oracle-buildpack,kirs/heroku-buildpack-nodejs,nikhil-bhandari/ng-cli-buildpack,karthikeyabhaghavatula/nodejs_buildpack,GoeGaming/heroku-buildpack-nodejs,ks2software/nodejs-buildpack,Ferrari/heroku-buildpack-nodejs,guilleva/heroku-buildpack-nodejs,Amandeepsinghghai/heroku-buildpack-nodejs,Jonatasmz/heroku-buildpack-nodejs,Scalingo/nodejs-buildpack,heroku/heroku-buildpack-nodejs,oocl-ncc-itm/nodejs-buildpack,marnold6/nodejs_buildpack,caiorogerio/heroku-buildpack-grunt,shoetomydixi/node_sigma_zapp_buildpack,Grahahax/nodejs-buildpack,ShreyasWao/heroku-buildpack-nodejs,simonjjones/snowedjs_buildpack,oocl-ncc-itm/nodejs-buildpack,goodeggs/heroku-buildpack-nodejs,cloudfoundry/nodejs-buildpack,Scalingo/nodejs-buildpack,cloudfoundry/nodejs-buildpack,raghuveerthummeti/nodejs-buildpack,ShakrMedia/heroku-buildpack-nodejs,bionikspoon/annotation-tool-heroku-buildpack-nodejs,diegobent/heroku-buildpack-nodejs,totapari/heroku-buildpack-nodejs,mikeyoon/heroku-buildpack-nodejs,shedd/heroku-buildpack-nodejs,NSWIDER/nodejs-oracle-buildpack,ks2software/nodejs-buildpack,Hylozoic/heroku-buildpack-nodejs-babel,Scalingo/nodejs-buildpack,roder/nodejs-buildpack,ks2software/nodejs-buildpack,marnold6/nodejs_buildpack,roder/nodejs-buildpack,Scalingo/nodejs-buildpack,kudos/heroku-buildpack-nodejs-jspm,cloudfoundry/nodejs-buildpack,heroku/heroku-buildpack-nodejs,mmgm/nodejs-buildpack,mrc535s/wkhtmltopdfbp,apiaryio/heroku-buildpack-nodejs-grunt,pkumar-appd/nodejs-buildpack,NSWIDER/nodejs-oracle-buildpack,salesforceidentity/heroku-buildpack-nodejs-jdk8,glawson6/heroku-buildpack-nodejs,ks2software/nodejs-buildpack,bionikspoon/heroku-buildpack-nodejs,heroku/heroku-buildpack-nodejs,marnold6/nodejs_buildpack,JasonZigelbaum/heroku-buildpack-nodejs,yookoala/heroku-buildpack-nodejs,simonjjones/snowedjs_buildpack,cloudControl/buildpack-nodejs,raghuveerthummeti/nodejs-buildpack,mmgm/nodejs-buildpack,The18thWarrior/ethereum-buildpack,justinwalsh/heroku-buildpack-nodejs,raghuveerthummeti/nodejs-buildpack,simonjjones/snowedjs_buildpack,tweettypography/heroku-buildpack-nodejs,TheHealthPros/heroku-buildpack-nodejs,mmgm/nodejs-buildpack,sailrish/heroku-buildpack-nodejs,oocl-ncc-itm/nodejs-buildpack,caiorogerio/heroku-buildpack-grunt,tamdao/heroku-buildpack-nodejs,tomfa/heroku-buildpack-nodejs,Jell-E/heroku-buildpack-nodejs-rust,CloudSide/heroku-buildpack-nodejs