install_toolchain: change warn to echo in sudo context

This code runs in sudo context which doesn't have access to common.sh
shell helpers.  Use an echo instead.

BUG=chromium:395265
TEST=setup_board w/injected errors shows the warning message

Change-Id: I12c9cb7ca97d6c09433419e65a478a6d12bf86f2
Reviewed-on: https://chromium-review.googlesource.com/227262
Reviewed-by: Vadim Bendebury <vbendeb@chromium.org>
Commit-Queue: Mike Frysinger <vapier@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>
1 file changed