github: enable cron schedule

Since GH is mirroring the code directly from our GoB systems, they
aren't triggering push events.  Set them up with a daily/weekly cron
so we get some level of coverage.

Change-Id: I9ececc74a4904e0e3060a10ee1acb952e2021240
Reviewed-on: https://chromium-review.googlesource.com/c/breakpad/breakpad/+/3289899
Reviewed-by: Mark Mentovai <mark@chromium.org>

.github/workflows/build-test-ci.yml

@@ -7,6 +7,14 @@ on:
   push:
     branches: [main]
 
+  schedule:
+    # The GH mirroring from Google GoB does not trigger push actions.
+    # Fire it every other day to provide some coverage.  This will run ~8 AM PT.
+    - cron: '39 3 */2 * *'
+
+  # Allow for manual triggers from the web.
+  workflow_dispatch:
+
 jobs:
   autotools:
     strategy:

.github/workflows/coverity.yml

@@ -8,6 +8,14 @@ on:
   push:
     branches: [main]
 
+  schedule:
+    # The GH mirroring from Google GoB does not trigger push actions.
+    # Fire it once a week to provide some coverage.
+    - cron: '39 2 * * WED'
+
+  # Allow for manual triggers from the web.
+  workflow_dispatch:
+
 jobs:
   coverity:
     runs-on: ubuntu-latest