cros_bundle_firmware: Add new progress message after GBB

At present it looks like we take ages to produce the GBB. Add a new
progress message to fix that.

BUG=none
BRANCH=none
TEST=manual
Run cros_bundle_firmware as normal and check that the new messages
appears.

Change-Id: I0fac39d0b41631090076a076d3558d87a0abcbd8
Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/39875
Reviewed-by: Randall Spangler <rspangler@chromium.org>
diff --git a/host/lib/bundle_firmware.py b/host/lib/bundle_firmware.py
index d5e9613..cb675e5 100644
--- a/host/lib/bundle_firmware.py
+++ b/host/lib/bundle_firmware.py
@@ -1008,6 +1008,7 @@
     for blob_type in pack.GetBlobList():
       self._BuildBlob(pack, fdt, blob_type)
 
+    self._out.Progress('Packing image')
     if gbb:
       pack.RequireAllEntries()
       fwid = '.'.join([