The compilation of the candidate of NWCHEM6.8 on macOS Sierra 10.12.6 with gfortran6.3.0,
mpich 3.2_2 and Xcode 9.1 installed fails because of the following error
...
ld: library not found for -lSystem
collect2: error: ld returned 1 exit status
make: *** [all] Error 1