testing/seatd: log to file

previously logs were just discarded
7 jobs for !20432 with seatd in 27 seconds (queued for 1 second)
merge request
Name Stage Failure
failed
build-x86 Build
No job log
failed
build-ppc64le Build
No job log
failed
lint Lint
No job log
failed
build-x86_64 Build
No job log
failed
build-s390x Build
No job log
failed
build-aarch64 Build
No job log
failed
build-armv7 Build
No job log