`gleam compile-package` no longer produces erlang files (nightly)

Hi!

gleam compile-package is used by other tools to integrate with Gleam. For this, it's quite common for them to search for the produced Erlang source code files, compiling them with their own respective toolchains.

Nightly removed those, producing .abstr files instead. This breaks all the tools relying on the output of compile-package. I think compile-package should continue to produce .erl files, and put .abstr files behind an optional flag, if at all.

~