Fix compiler when using ERL_COMPILER_OPTIONS=deterministic

[msaraiva]

According to the Erlang docs, Using the deterministic options will:

Omit the options and source tuples in the list returned by Module:module_info(compile)

Currently, the Surface compiler uses module_info/1 to retrieve the related source file in order to generate JS hooks. Instead, we could add/retrieve this information directly to/from the beam chunks as an custom attribute so we're able to use deterministic.

[ju1m]

The current approach assumes something more than not having ERL_COMPILER_OPTIONS=deterministic, namely that the source given by module_info still exists, which is not the case when building each mix app in ephemeral sandboxes like nix does by default.
See in nix the source is deterministically in /build/source/, but actually exists only during the build of the mix app:

iex(1)> Bonfire.UI.Me.Stickyheader.module_info() |> get_in([:compile])
[
  version: ~c"9.0.2",
  options: [:no_spawn_compiler_process, :from_core, :no_core_prepare,
   :no_auto_import],
  source: ~c"/build/source/lib/components/profile/stickyheader.ex"
]

So that by the time the dependency (Bonfire.UI.Me.Stickyheader) is used (through $ERL_LIBS), its /build/source/ is long gone (actually it's now the /build/source/ of the current mix app using that dependency).

[ju1m]

When using nixpkgs's buildMix, a workaround is to build into $out/src/ instead of /build/source/, so that module_info returns a path inside $out, which, being the final output path of the package into the Nix store, still exists when building dependent packages:

buildMix {
   erlangDeterministicBuilds = false;

   # Explanation: sadly disabling erlangDeterministicBuilds is not enough
   # for `mix compile.surface` to work across packages, as it:
   # - needs to access the content of the source path of the dependencies,
   # - and, uses as source path the actual path where the dependencies were built.
   # Since buildMix's installPhase only copies $src into $out/src,
   # that is not enough: module_info/1 will return /build/source instead of $out/src,
   # so build into $out/src, which will remain reachable after the build.
   # Issue: https://github.com/surface-ui/surface/issues/762#issuecomment-3577030748
   postUnpack = previousArgs.postUnpack or "" + ''
     mkdir -p $out
     mv $sourceRoot $out/src
     sourceRoot=$out/src
     src=$(mktemp -d)
   '';
   postInstall = previousArgs.postInstall or "" + ''
     src=$out/src
     rm -rf _build
   '';

  […snip…]
}

Which now records an existing source:, enabling compile.surface to correctly generate all the .hooks.js of the dependencies:

iex(1)> Bonfire.UI.Me.Stickyheader.module_info() |> get_in([:compile])
[
  version: ~c"9.0.2",
  options: [:no_spawn_compiler_process, :from_core, :no_core_prepare,
   :no_auto_import],
  source: ~c"/nix/store/xhkblhd0jnw3ynvyk66jf9cglyh2h5lb-bonfire_ui_me-0.1.0/src/lib/components/profile/stickyheader.ex"
]