Different company, maybe different problem, but importing code at Facebook was similarly difficult. The build issues were the least of it. More significant by far were the all-but mandatory requirements to integrate with the in-house deployment infrastructure, service discovery, background-task scheduling, metrics, logs, alerts, data structure libraries, RPC framework, etc. Your project already implemented some of those internally, or used open-source alternatives? Too bad. You could keep the core logic, but practically everything about how it connected to the rest of the world would have to be rewritten. Often, it just wasn't worth it, and a new "FB native" service reimplementing the same functionality was easier. If you didn't do it yourself, some other group would constantly be threatening to do it for you. It's hard to focus on code when you continually have to justify your project's very existence.
