Try the whole command line from my current cfg:
cmd_obj: x86_64-w64-mingw32-gfortran -cpp -march=native -O3 -c -fno-range-check -ffixed-line-length-132 -finit-real=nan -frecord-marker=4 -DHAVE_MPI -DHAVE_MUMPS <mods> <incs> <f95name>
cmd_exe: x86_64-w64-mingw32-gfortran -static -march=native -O3 -fno-range-check -ffixed-line-length-132 -finit-real=nan -frecord-marker=4 -v -o <exename> <objs> -Xlinker --start-group <libs>
I am using v7p3r1 with gcc-8.1 and everything compile and work fine.
**EDIT: Just make sure to delete the parts referring to MPI, -DHAVE_MPI and -DHAVE_MUMPS.
Costas