Odoo.sh will create a new build for every new commit. You can change this behavior from the SETTINGS tab of the branch:

Here, you can mute the branch. If you click on the Ignore new commits checkbox, Odoo.sh will stop listening to the new commits and it will not generate any more new builds. The other option is Behavior upon new commits. Changing this option will update the existing build instead of creating a new build for a new commit.