GitHub actions: cancel previous builds of same branch

[sbidoul]

When there are successive pushes to a given branch or PR, cancel running jobs on the same branch.

[github-actions]

There hasn't been any activity on this issue in the past 6 months, so it has been marked as stale and it will be closed automatically if no further activity occurs in the next 30 days.
If you want this issue to never become stale, please ask a PSC member to apply the "no stale" label.