How exactly does Epic build the binary distribution of the engine?

How exactly does Epic build the binary distribution of the engine?

I keep finding weird discrepancies with my source build of the engine.

Like when packaging to Android the whole game framework is recompiled each time. On the Binary version of the engine however, it just does incremental builds.

I really just want to replicate the binary build of the engine as close as possible with my source build.

Thanks,

James