Rebar3: Compile explicitly our Elixir files when --enable-elixir

Makefile.in

@@ -124,6 +124,7 @@ else
 ifeq ($(REBAR_ENABLE_ELIXIR),true)
   ELIXIR_LIBDIR_RAW=$(shell elixir -e "IO.puts(:filename.dirname(:code.lib_dir(:elixir)))" -e ":erlang.halt")
   ELIXIR_LIBDIR=":$(ELIXIR_LIBDIR_RAW)"
+  EXPLICIT_ELIXIR_COMPILE=MIX_ENV=default mix compile.elixir
 endif
 ifeq "$(REBAR_VER)" "3"
   SKIPDEPS=
@@ -179,6 +180,7 @@ $(DEPSDIR)/.built: $(DEPSDIR)/.got
 
 src: $(DEPSDIR)/.built
 	$(REBAR) $(SKIPDEPS) compile
+	$(EXPLICIT_ELIXIR_COMPILE)
 
 update:
 	rm -rf $(DEPSDIR)/.got

rebar.config

@@ -240,6 +240,7 @@
                    {mkdir, "conf"},
                    {copy, "rel/files/erl", "erts-\{\{erts_vsn\}\}/bin/erl"},
                    {template, "ejabberdctl.template", "bin/ejabberdctl"},
+                   {copy, "_build/default/lib/ejabberd/ebin/Elixir.*", "lib/ejabberd-{{release_version}}/ebin/"},
                    {copy, "inetrc", "conf/inetrc"},
                    {copy, "tools/captcha*.sh", "lib/ejabberd-\{\{release_version\}\}/priv/bin/"},
                    {copy, "rel/files/install_upgrade.escript", "bin/install_upgrade.escript"}]}