Adding Google Guava to Android project - significantly slows down the build
For what it's worth, my gut is that this isn't the cause. It's hard to take a long time doing anything with a mere 1.1MB of bytecode; I've never noticed dex taking any significant time. But let's assume it is the issue for sake of argument.
If it matters enough, you could probably slice up the Guava .jar to remove whole packages you don't use. It is composed of several pieces that aren't necessarily all inter-related.
I don't think this is going to speed things up, but maybe worth mentioning: if you run the build through Proguard (the optimizer now bundled with the SDK), it can remove unused classes before you get to DEX (and, do a bunch of other great optimization on the byte code). But of course that process probably takes longer itself than dex-ing.