clan: add run_no_stdout function suppressing stdout

Add the `run_no_stdout` function suppressing stdout by default.
This keeps the noise down on most commands, while still staying
debuggable.
Stdout will be active when the `--debug` flag is passed to the cli.

Fixes #1443

pkgs/clan-cli/clan_cli/config/parsing.py

@@ -2,7 +2,7 @@ import json
 from pathlib import Path
 from typing import Any
 
-from ..cmd import run
+from ..cmd import run_no_stdout
 from ..errors import ClanError
 from ..nix import nix_eval
 
@@ -32,7 +32,7 @@ def schema_from_module_file(
     """
     # run the nix expression and parse the output as json
     cmd = nix_eval(["--expr", nix_expr])
-    proc = run(cmd)
+    proc = run_no_stdout(cmd)
     return json.loads(proc.stdout)