Remove REBAR_BARE_COMPILER_OUTPUT_DIR to fix issues with build_embedded

See #10978.

Author: josevalim

lib/mix/lib/mix/tasks/deps.compile.ex

@@ -197,11 +197,9 @@ defmodule Mix.Tasks.Deps.Compile do
     config_path = Path.join(dep_path, "mix.rebar.config")
     lib_path = Path.join(config[:env_path], "lib/*/ebin")
 
-    # REBAR_BARE_COMPILER_OUTPUT_DIR is only honored by rebar3 >= 3.14
     env = [
       {"REBAR_CONFIG", config_path},
-      {"TERM", "dumb"},
-      {"REBAR_BARE_COMPILER_OUTPUT_DIR", dep_path}
+      {"TERM", "dumb"}
     ]
 
     cmd = "#{rebar_cmd(dep)} bare compile --paths #{lib_path}"