Add Updater Packaging to unsigned build output.

Bug: 1024318
Change-Id: I600616ea823fe398f58c18622c0a4831a17426f5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2116570
Commit-Queue: Joshua Pawlicki <waffles@chromium.org>
Commit-Queue: Robert Sesek <rsesek@chromium.org>
Auto-Submit: Joshua Pawlicki <waffles@chromium.org>
Reviewed-by: Robert Sesek <rsesek@chromium.org>
Cr-Commit-Position: refs/heads/master@{#752545}

chrome/tools/build/mac/FILES.cfg

@@ -145,4 +145,10 @@ FILES = [
     'buildtype': ['official'],
     'archive': 'updater.zip',
   },
+  {
+    'filename': 'Updater Packaging',
+    'buildtype': ['official'],
+    'archive': 'updater.zip',
+    'optional': ['official'], # TODO(crbug.com/1024318): Make non-optional.
+  },
 ]