...
The key '-j4' makes the command use 4 cores in parallel. But you can also run it on one core only with:
make work
4) Use your executable
To use your own executable set 'GEM_ovbin' in your 'configexp.cfg' to the path of your executable directory, up until but excluding the 'gem' directory. For example:
GEM_ovbin=~/gem/v_5.1.1/Abs/my_abs