Print progress messages for finished builds

To identify builds that do not finish in time print a messages
whenever one of the subtasks is finished.

Change-Id: I67f59e22345f923c514a91fcbce2df057e2ef66c
Reviewed-on: https://cos-review.googlesource.com/c/cos/tools/+/24370
Cloud-Build: GCB Service account <228075978874@cloudbuild.gserviceaccount.com>
Reviewed-by: Robert Kolchmeyer <rkolchmeyer@google.com>
Reviewed-by: Arnav Kansal <rnv@google.com>
Tested-by: Oleksandr Tymoshenko <ovt@google.com>
diff --git a/cloudbuild.yaml b/cloudbuild.yaml
index 29afca5..99c7d2b 100644
--- a/cloudbuild.yaml
+++ b/cloudbuild.yaml
@@ -21,6 +21,8 @@
         if [[ $? -ne 0 ]]; then
           echo "$d failed" | tee -a ${failure_file}
           cat ${logfile}
+        else
+          echo "$d finished"
         fi
       ) &
     done