build: add global soft timeout of 12 hours
build: add global soft timeout of 12 hours

Only start new builds for 12 hours. This ensures we publish new builds
often enough even on long backlogs.

This could be made configurable at a later point.

f-droid/fdroid-server,f-droid/fdroidserver,fdroidtravis/fdroidserver,f-droid/fdroid-server,f-droid/fdroidserver,fdroidtravis/fdroidserver,f-droid/fdroidserver,f-droid/fdroidserver,fdroidtravis/fdroidserver,f-droid/fdroid-server,fdroidtravis/fdroidserver,f-droid/fdroid-server,f-droid/fdroid-server,f-droid/fdroidserver