Move env assignment into parseCommandLine

A bit of a misnomer but makes things more testable so I’ll accept it
until we can do more overhaul.

src/main-process/main.js

@@ -21,7 +21,6 @@ console.log = require('nslog')
 
 function start () {
   const args = parseCommandLine(process.argv.slice(1))
-  args.env = process.env
   setupAtomHome(args)
   setupCompileCache()
 

src/main-process/parse-command-line.js

@@ -130,7 +130,7 @@ module.exports = function parseCommandLine (processArgs) {
     resourcePath, devResourcePath, pathsToOpen, urlsToOpen, executedFrom, test,
     version, pidToKillWhenClosed, devMode, safeMode, newWindow, logFile, socketPath,
     userDataDir, profileStartup, timeout, setPortable, clearWindowState,
-    addToLastWindow, mainProcess
+    addToLastWindow, mainProcess, env: process.env
   }
 }