[Suicide Junkie]

It dosen't *prevent* it, but it does limit the usefulness of such a tactic.

For example, it does take a while to build up infrastructure on your colonies. The quick and cheap facilities are pretty weak.
You also don't really have a problem with build rate, since if build rate is an issue, you just notch down the size of the ships you're building to take advantage of the "Build Time = size squared".

In short, your homeworld can pretty much do most of everything on its own if nessesary. Colonies are an investment, not a license to print money.