WIP don't control concurrency from INSIDE_DUNE

Unfortuantely due to the way build forwarding warnings work we warn alot
since DUNE_JOBS differs from the default.

Signed-off-by: Ali Caglayan <alizter@gmail.com>

Author: Alizter

src/dune_config_file/dune_config_file.ml

@@ -484,7 +484,7 @@ module Dune_config = struct
 
   let default =
     { display = Simple { verbosity = Quiet; status_line = not Execution_env.inside_dune }
-    ; concurrency = (if Execution_env.inside_dune then Fixed 1 else Auto)
+    ; concurrency = Auto
     ; terminal_persistence = Clear_on_rebuild
     ; sandboxing_preference = []
     ; cache_enabled = Enabled_except_user_rules

test/blackbox-tests/test-cases/dune

@@ -3,6 +3,7 @@
   (env-vars
    (DUNE_CONFIG__BACKGROUND_SANDBOXES disabled)
    (DUNE_CONFIG__BACKGROUND_DIGESTS disabled)
+   (DUNE_JOBS 1)
    ;; We set ocaml to always be colored since it changes the output of
    ;; ocamlc error messages. See https://github.com/ocaml/ocaml/issues/14144
    (OCAML_COLOR always))
@@ -23,6 +24,7 @@
  (applies_to :whole_subtree)
  (deps
   (env_var OCAML_COLOR)
+  (env_var DUNE_JOBS)
   %{bin:dune_cmd}
   (package dune))
  ;; We don't allow conflict markers in tests