Fix global cache config overriding

There was some confusion in the code:

- `rebar_dir:global_config()` returns the default path
- `rebar_dir:global_config(State)` returns the configured path based on
  the ENV overrides, and defaults to `global_config()` if nothing is
  given

Since no State term existed at this point in time, we just called out
directly to the argument-free version of the call, but this ignored all
overrides. Instead, we call it with an initialized `rebar_state:new()` to
properly handle configuration from users, and then use the actual
configured state (if any).

src/rebar3.erl

@@ -207,17 +207,18 @@ init_config() ->
 
     Config = rebar_config:consult_root(),
     Config1 = rebar_config:merge_locks(Config, rebar_config:consult_lock_file(?LOCK_FILE)),
+    InitState = rebar_state:new(Config1),
 
     %% If $HOME/.config/rebar3/rebar.config exists load and use as global config
-    GlobalConfigFile = rebar_dir:global_config(),
+    GlobalConfigFile = rebar_dir:global_config(InitState),
     State = case filelib:is_regular(GlobalConfigFile) of
                 true ->
                     ?DEBUG("Load global config file ~ts", [GlobalConfigFile]),
                     try state_from_global_config(Config1, GlobalConfigFile)
                     catch
                         _:_ ->
                             ?WARN("Global config ~ts exists but can not be read. Ignoring global config values.", [GlobalConfigFile]),
-                            rebar_state:new(Config1)
+                            InitState
                     end;
                 false ->
                     rebar_state:new(Config1)