chore(build): pin port_compiler v1.11.1

Port compiler bug in v1.11.0:
In windows builds, cl.exe produces .obj files
link.exe looks for .o files to link.

rebar.config.erl

@@ -85,6 +85,9 @@ project_app_dirs() ->
 plugins(HasElixir) ->
     [ {relup_helper,{git,"https://github.com/emqx/relup_helper", {tag, "2.0.0"}}}
     , {er_coap_client, {git, "https://github.com/emqx/er_coap_client", {tag, "v1.0"}}}
+      %% emqx main project does not require port-compiler
+      %% pin at root level for deterministic
+    , {pc, {git, "https://github.com/emqx/port_compiler.git", {tag, "v1.11.1"}}}
     | [ rebar_mix || HasElixir ]
     ]
     %% test plugins are concatenated to default profile plugins