clippy: remove set -u to fix errors on older bash
clippy: remove set -u to fix errors on older bash

With versions of bash before 4.4 (such as bash 4.3 provided by the cros
sdk), expanding an empty array when `set -u` is in effect causes an
error:

  bin/clippy: line 93: CLIPPY_ARGS[@]: unbound variable

This could be avoided by testing the CLIPPY_ARGS variable before
expanding it, but this is such a small and simple script that removing
`set -u` seems more appropriate.

BUG=chromium:1105466
TEST=`bin/clippy` with no args inside cros_sdk

Change-Id: Id56a99bf23f3d9b97b6b7f8a62dce95f9112caa6
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/2324061
Tested-by: Daniel Verkamp <72bc170b46ec491f7bdd4359a1c0bfed274de40c@chromium.org>
Reviewed-by: Mike Frysinger <8f3f75c74bd5184edcfa6534cab3c13a00a2f794@chromium.org>
Reviewed-by: Keiichi Watanabe <815e4e8f7c92a23424d7c3f51ead622bcedbc720@chromium.org>
Reviewed-by: Zach Reizner <3374927928a53d04457674c546bd4de57c2044ec@chromium.org>
Commit-Queue: Keiichi Watanabe <815e4e8f7c92a23424d7c3f51ead622bcedbc720@chromium.org>

google/crosvm,google/crosvm,google/crosvm,google/crosvm