Add render process check for ATOM_HOME

Setting it in the browser process does not seem to make it into
the render processes on Linux.

Closes #5412

src/window-bootstrap.coffee

@@ -1,3 +1,14 @@
+# Ensure ATOM_HOME is always set before anything else is required
+unless process.env.ATOM_HOME
+  if process.platform is 'win32'
+    home = process.env.USERPROFILE
+  else
+    home = process.env.HOME
+  atomHome = path.join(home, '.atom')
+  try
+    atomHome = require('fs').realpathSync(atomHome)
+  process.env.ATOM_HOME = atomHome
+
 # Like sands through the hourglass, so are the days of our lives.
 require './window'