build(emqx): fix emqx standalone dialyzer

apps/emqx/rebar.config

@@ -24,7 +24,6 @@
 
 {plugins, [rebar3_proper]}.
 {extra_src_dirs, [{"etc", [recursive]}]}.
-
 {profiles, [
    {test,
        [{deps,
@@ -36,3 +35,13 @@
          {extra_src_dirs, [{"test",[recursive]}]}
        ]}
 ]}.
+
+{dialyzer, [
+    {warnings, [unmatched_returns, error_handling, race_conditions]},
+    {plt_location, "."},
+    {plt_prefix, "emqx_dialyzer"},
+    {plt_apps, all_apps},
+    {plt_extra_apps, [hocon]},
+    {statistics, true}
+   ]
+}.