Add script for gsi_pubsign build chaining target

Bug: 149803895
Test: ./gsi-pubsign-release.sh aosp_arm64 aosp_arm64_pubsign \
        aosp_arm64-artifact_path aosp_arm64_pubsign-artifact_path

Merged-In: I05e82f0605eec33c0da9b5a5d5cbf3506af3706c
Change-Id: I05e82f0605eec33c0da9b5a5d5cbf3506af3706c
(cherry picked from commit 45c81a65e7511299fae1d3a8c53852b7d769f80c)
1 file changed