feat(bin/emqx): make possible to boot Erlang node from Elixir build

bin/emqx

@@ -872,9 +872,12 @@ case "${COMMAND}" in
               --erl "$EPMD_ARGS" \
               --werl
         else
+          # pass down RELEASE_LIB so we can switch to IS_ELIXIR=no
+          # to boot an Erlang node from the elixir release
           set -- "$BINDIR/erlexec" \
               $FOREGROUNDOPTIONS \
               -boot "$BOOTFILE" \
+              -boot_var RELEASE_LIB "$ERTS_LIB_DIR" \
               -boot_var ERTS_LIB_DIR "$ERTS_LIB_DIR" \
               -mode "$CODE_LOADING_MODE" \
               -mnesia dir "\"${MNESIA_DATA_DIR}\"" \

rel/emqx_vars

@@ -11,7 +11,7 @@ RUNNER_LOG_DIR="{{ runner_log_dir }}"
 RUNNER_LIB_DIR="{{ runner_lib_dir }}"
 EMQX_ETC_DIR="{{ emqx_etc_dir }}"
 RUNNER_USER="{{ runner_user }}"
-IS_ELIXIR="{{ is_elixir }}"
+IS_ELIXIR="${IS_ELIXIR:-{{ is_elixir }}}"
 SCHEMA_MOD="{{ emqx_schema_mod }}"
 IS_ENTERPRISE="{{ is_enterprise }}"