Don't copy OEM image to partition if it doesn't exist

BUG=none
TEST=Run build_image for sonic, verify it doesn't fail

Change-Id: I6be223faecc7322894ddcdbba3bbac2a4e52e0a7
Reviewed-on: https://gerrit.chromium.org/gerrit/64716
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Commit-Queue: Liam McLoughlin <lmcloughlin@google.com>
Tested-by: Liam McLoughlin <lmcloughlin@google.com>
1 file changed