adds a container setting to build job

Author: arcra

.github/workflows/ci.yml

@@ -38,6 +38,7 @@ jobs:
     # Other workflows are likely ok to use standard GH runners for now.
     # Googlers, see b/460874304.
     runs-on: linux-x86-n2-32
+    container: jobs.build.container
     needs: lint-python-flake8 # fail fast in case of "undefined variable" errors
     strategy:
       fail-fast: false