rebar3Relx: add executable to bin dir and remove unnecessary dependency

pkgs/development/beam-modules/rebar3-release.nix

@@ -82,9 +82,20 @@ let
             else "rel"}
       mkdir -p "$out/$dir"
       cp -R --preserve=mode "_build/${profile}/$dir" "$out"
+      ${lib.optionalString (releaseType == "release")
+      "mkdir -p $out/bin && ln -s -t $out/bin $out/rel/*/bin/*"}
       runHook postInstall
     '';
 
+    postInstall = ''
+      for dir in $out/rel/*/erts-*; do
+        echo "ERTS found in $dir - removing references to erlang to reduce closure size"
+        for f in $dir/bin/{erl,start}; do
+          substituteInPlace "$f" --replace "${erlang}/lib/erlang" "''${dir/\/erts-*/}"
+        done
+      done
+    '';
+
     meta = {
       inherit (erlang.meta) platforms;
     } // meta;