Slicer 4.10.0 with Qt4.8 and VTK 7 is built from source successfully on Ubuntu 18.04 but I had to add this line to the main CMakeList.txt file due to some error related to c11 support.
set (CMAKE_CXX_STANDARD 11)
after these two lines
set(_msg "Setting C++ standard")
message(STATUS "${_msg}")
Yes, parallel builds work fine, but often the actual build error is hard to see because other build output causes it to scroll offscreen. In this case I often use a command like make -j20; make so the actual error shows up efficiently.
Thanks for the tips. The build just completed without error. It seems the previous one had some strange problem. Next step, test building on Windows 10.