I managed to build 1.0.8 on Ubuntu 16.04 but I had to make a directory called "CL" in the main directory and copy "cl.hpp" file from my old 1.0.7 build folder in there. Looks like that folder and file are missing from github.
I removed it from the repo because on Windows it's loaded from external dependencies. Shouldn't it be part of the OpenCL ICD?