build_artifact: select correct signed image

xbuddy has a concept of "signed" image, but there are actually
a number of signed artifacts. The only one you'd be likely to
want to flash to USB would be the recovery image though.

This regex specifies that this should be a recovery image.

Example failing case:
xbuddy://remote/flapjack/latest-canary/signed ->
chromeos_12185.0.0_flapjack_factory_canary-channel_premp.bin,
chromeos_12185.0.0_flapjack_recovery_canary-channel_premp.bin
Currently fails due to two matches. Retreives the correct
image with this change.

BUG=chromium:959044
TEST=cros flash usb:// xbuddy://remote/flapjack/latest-canary/signed

Change-Id: If9c4d545246aea3f99196cbb2a544db9f064da90
Reviewed-on: https://chromium-review.googlesource.com/1600464
Commit-Ready: Nick Sanders <nsanders@chromium.org>
Tested-by: Nick Sanders <nsanders@chromium.org>
Legacy-Commit-Queue: Commit Bot <commit-bot@chromium.org>
Reviewed-by: Congbin Guo <guocb@chromium.org>
Reviewed-by: Amin Hassani <ahassani@chromium.org>
1 file changed