Delete the files in build/android-profile
(It contains .rawproto and .json files)
After doing this you may see monstrous speed increases. One of the reasons for the slowdown may be Lint checking these files during the build. The folder had grown to 2GB on my computer and contained over 7000 files. That can't be good. I guess an alternative approach could be to configure Lint to ignore this folder, but I haven't investigated any further.
Warning: I am not completely sure whether these files have any value, so you can check for yourself. You definitely don't need them in order to build the project, that's for sure (you don't check them in GIT anyway).