Create separate archive of Mac packaging tools.

This is in preparation for separating diff creation from signing,
similar to the Windows processing, and needed by the new signing
pipeline.

R=mark@chromium.org
BUG=b/31931170

Review-Url: https://chromiumcodereview.appspot.com/2432933006
Cr-Commit-Position: refs/heads/master@{#426800}

chrome/tools/build/mac/FILES.cfg

@@ -38,6 +38,11 @@ FILES = [
     'filename': 'Google Chrome Packaging',
     'buildtype': ['official'],
   },
+  {
+    'filename': 'Google Chrome Packaging',
+    'buildtype': ['official'],
+    'archive': 'packaging.zip',
+  },
   # PNaCl translator (archive only, component updater used for shipping).
   {
     'filename': 'pnacl',