I closely followed README.md. On the final stage, sgw and pgw did not start since pgw executable was missing and sgw executable was called differently. This is because fresh version of master was built rather than 1.2.0, and executables in the fresh version are named differently.
To build ver. 1.2.0, I had to download the old version rather than fresh master, then patch 3 files.
My README with updated instruction is here.