Build processing no longer fails when duplicate jobs collide on a shared temp file

Fixes a race condition where two concurrent build-processing jobs for the same build would share the temp download path /tmp/build_<build_id>.zip. One job’s download or cleanup could overwrite or delete the archive the other was still unzipping, producing a spurious “doesn’t seem like a valid SLF line” failure even though the stored archive was valid. The temp path is now keyed on a per-execution unique integer, so duplicate jobs for the same build no longer collide.