Ran out of RAM for cloud builds - Google generally does not use virtual memory for anything in the cloud, because it leads to unpredictable, massive delays which can cause cascading failures in services.
It was still "possible" to build on your workstation, but the locality patterns in linking and subsequent thrashing made this extremely an extremely small value of "possible". I recall once during this period I kicked off a local debug build on my workstation on Friday afternoon, went home for the weekend, and it was still running when I got into work on Monday morning. By Tuesday, I had given up and killed it.
