Updater: Upload signing scripts and auxiliaries to unsigned builds dir.

This also packages the updater.exe into the same zip. From here, we'll
build a thin signing pipeline in the signing service to unpack the zip
and run the code.

The .exe upload can be removed later once the new system is working.

Bug: 926234
Change-Id: Ia23999927519fa93b9164bfac42357d41ae6c422
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2443216Reviewed-by: Michael Moss <mmoss@chromium.org>
Commit-Queue: Joshua Pawlicki <waffles@chromium.org>
Cr-Commit-Position: refs/heads/master@{#813293}

chrome/tools/build/win/FILES.cfg

@@ -711,12 +711,19 @@ FILES = [
   {
     'filename': 'updater.exe',
     'buildtype': ['official'],
-    'archive': 'updater.exe',
+    'optional': ['official'], # TODO(crbug.com/926234): Remove optional.
+    'archive': 'updater.zip',
   },
   {
-    'filename': 'UpdaterSetup.exe',
+    'filename': 'UpdaterSigning',
     'buildtype': ['official'],
-    'archive': 'UpdaterSetup.exe',
+    'optional': ['official'], # TODO(crbug.com/926234): Remove optional.
+    'archive': 'updater.zip',
+  },
+  { # TODO(crbug.com/926234): Remove this upload after server side is updated.
+    'filename': 'updater.exe',
+    'buildtype': ['official'],
+    'archive': 'updater.exe',
   },
   # Partner API files.
   {