vboot/sign_official_build: Fix missing backslash

Add the missing line continuation backslash, caused by CL:3046439.

BUG=b:198232639
TEST=./sign_official_build.sh recovery ${IMAGE} tests/devkeys/ ${OUTPUT}
TEST=./sign_official_build.sh factory ${IMAGE} tests/devkeys/ ${OUTPUT}
BRANCH=none

Change-Id: I587747e33c47afc85264052c9ca59081d5524a72
Signed-off-by: Yu-Ping Wu <yupingso@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/vboot_reference/+/3134894
Reviewed-by: Julius Werner <jwerner@chromium.org>
Commit-Queue: Julius Werner <jwerner@chromium.org>
1 file changed