4. The compiler should not be included and neither should the headers. Unless a user explicitly wants to include the compiler and also have a C compiler on the node in order to compile stuff on the target node there is no reason to have the header files there and relups work fine without them.
If Elixir 1.11 'mix release' still includes all of the `erts` directory then an issue should be opened.
Yeah, it doesn’t include it all the time. It’s an option, though, and one that the OP might have accidentally been using. (I think in relx there’s an explicit `include_src` flag you pass to enable it.) I was just justifying the presence of the option. It’s not always, or even usually necessary.
Not a big deal but, it was actually a bug in relx that caused it to be included (accidentally copying the erts dir from the symlink/copy in the _build/<profile>/rel/<relname>/ dir instead of from the unpacked tarball generated by systools when doing the final assembly), not `include_src`, that option only applies to the Erlang applications and not the runtime.
If Elixir 1.11 'mix release' still includes all of the `erts` directory then an issue should be opened.