CHROMIUM: disable --depclean warnings

We never use --depclean, so stop showing it to devs.  It will most
likely do the wrong thing for them anyways.

BUG=None
TEST=CQ passes

Change-Id: Ic3ec223d260935973b3b04199b12e5b60c57e801
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/portage_tool/+/3383441
Reviewed-by: Chris McDonald <cjmcdonald@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>
Commit-Queue: Mike Frysinger <vapier@chromium.org>
2 files changed