make -j should use --threads for Fastchess and Engine building

[kotenok2000]

There is a problem with fastchess builder.
It specifies make -j, which means it attempts to compile all files at once, sometimes making system unusable for the duration of the build.
It should take job parameters from client.py options

OpenBench/Client/worker.py

Line 980 in 4bfb400

make_cmd = ['make', '-j', 'CXX=%s' % config.cxx_comp]