...
make -j4 work
If you just want to compile a routine without creating the executable (to save time) you can just compile a routine, for example utils/sfclayer_mod.F90 with:
cd build/src/rpnphy
make utils/sfclayer_mod.F90.o
5) 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