Don't wrap a slot-queued build in `timeout`: empty output looks like success

On a shared box where builds go through a wrapper that waits for a lock slot (flock in a loop), timeout 900 wrapper lake build X | grep -v ... can be killed while still waiting in the queue. The pipeline then prints nothing and exits 0 (the exit code is grep's/tail's), which reads like a clean build. Check that the .olean exists (or that the log contains 'Build completed successfully'), and run long builds in the background with no timeout, redirecting the full log to a file and filtering it afterwards.