dim: Fix shellcheck SC2153

The fix is a bit artificial, but mute the warning.

Fixes: 809748225c4e ("dim: Add add-missing-cc command")
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>