Set --quiet when run under gemini-cli

Bug: 436540341
Change-Id: Ic04ba12e0bcb926b90dd5dfbd3df4685cf59535a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/6832667
Reviewed-by: Andrew Grieve <agrieve@chromium.org>
Reviewed-by: Junji Watanabe <jwata@google.com>
Commit-Queue: Erik Staab <estaab@chromium.org>

autoninja.py

@@ -252,6 +252,14 @@ def _convert_ninja_j_to_siso_flags(j_value, use_remoteexec, args):
 
 
 def _main_inner(input_args, build_id):
+    # If running in the Gemini CLI, automatically add --quiet if it's not
+    # already present to avoid filling the context window.
+    if os.environ.get('GEMINI_CLI') == '1':
+        if not any(arg in ('--quiet', '-q') for arg in input_args):
+            print('Adding --quiet because we\'re running under gemini-cli ('
+                  'GEMINI_CLI=1)')
+            input_args.append('--quiet')
+
     # if user doesn't set PYTHONPYCACHEPREFIX and PYTHONDONTWRITEBYTECODE
     # set PYTHONDONTWRITEBYTECODE=1 not to create many *.pyc in workspace
     # and keep workspace clean.