Node 12+ has access to `globalThis` (including within a VM context), but
older versions do not.

Due to the detection done in https://git.io/Jtb7s, when we can't find
`globalThis` (and don't define `global` global) evaluating
`ember-template-compiler.js` throws an error "unable to locate global
object".

This ensures that either `globalThis` or `global` are defined.