Add missing comments in `cloud_build.py`.
Add missing comments in `cloud_build.py`.

PiperOrigin-RevId: 397958645
Change-Id: I2f2c1265720cb435911319e22495460e054d5149
GitOrigin-RevId: 5c120d1420ba44bace74eff00e3d2a70fd5b6071

deepmind/xmanager,deepmind/xmanager