Unbearable compile times

I have just started trying to make a change to the Unreal Engine. I know, that C++ projects can take some time compiling for the first time. So I compiled the project and waited for about 2 hours for it to finish. Then I made my change to APlayerController and compiled again. To my surprise the build tool decided to compile the whole project again. As far as I can see, it’s compiling more than 500 Dlls. Why? Is there a way to speed this up? I don’t have the time to wait hours on end for this thing to finish.

Disable Unity, enable fast iteration and consider IncrediBuild as an option to use all computers you can access for compilation.

I tried turning off the Unity build and now it’s taking even longer. I hope this is only a one time thing, until it has recompiled the whole thing. I will have to set up a separate machine just for release builds, so that I don’t have to switch build types on my development computer.
Are there any free continuous integration solutions that work with UE?

Ya its slow I know everything about it. And when you touch a header file that is included all around it will still compile every source file under the sun, so I kept unity builds on because it will eventually be faster.

If I start swearing on my comp about it then its ventilation activity goes down (because its doing god knows what but not compiling anymore), so it comes with daemons too. lol