[Packager] naïve concatenation of JS files breaks things

[michaelficarra]

See tvcutsem/harmony-reflect#47 (comment). A safe way to concatenate JS files would be to join on "\n;", but that is not robust against potential future additions to the language (such as allowing unclosed trailing multiline comments).

[amasad]

What's the ideal way to do it?

[michaelficarra]

For scripts, there's no reliable way to combine two into the same file and preserve all semantics. For modules, you can just parse both programs and append the module items of the latter program to those of the former.