can't compile using only `--with-stars=GEAR --with-hydro=default`

Opening this issue by request of @lhausammann Apparently I need to specify --with-star-formation=GEAR as well.

Compiled with

 --with-parmetis --with-jemalloc --with-hdf5=/home/mivkov/local/spack/opt/spack/linux-ubuntu18.04-skylake/gcc-8.3.0/hdf5-1.10.5-mqqg7t7wlchbz4ph5uz5mbcg4k7tfwxf/bin/h5pcc --enable-mpi=no --disable-doxygen-doc --program-suffix=-rt-tasking --enable-cell-graph --with-stars=GEAR --with-hydro=default --enable-task-debugging --enable-threadpool-debugging

First error I got was

In file included from ./black_holes/Default/black_holes_io.h:23,
                 from black_holes_io.h:29,
                 from single_io.c:39:
./stars/GEAR/stars_io.h: In function 'stars_read_particles':
./stars/GEAR/stars_io.h:51:48: error: 'struct star_formation_spart_data' has no member named 'birth_mass'
                                 sparts, sf_data.birth_mass);
                                                ^
./io_properties.h:183:43: note: in definition of macro 'io_make_input_field'
                        (char*)(&(part[0]).field), sizeof(part[0]))
                                           ^~~~~
make[3]: *** [libswiftsim_la-line_of_sight.lo] Error 1

However, for some reason I can't reproduce this error at the moment. Currently I'm getting

In file included from part.h:110,
                 from space.h:36,
                 from space.c:40:
./stars/GEAR/stars_part.h:92:31: error: field ‘chemistry_data’ has incomplete type
   struct chemistry_spart_data chewith-hdf5=/home/mivkov/local/spack/opt/spack/linux-ubuntu18.04-skylake/gcc-8.3.0/hdf5-1.10.5mistry_data;
                               ^~~~~~~~~~~~~~
In file included from stars.h:33,
                 from space.c:67:
./stars/GEAR/stars.h: In function ‘stars_first_init_spart’:
./stars/GEAR/stars.h:71:14: error: ‘struct star_formation_spart_data’ has no member named ‘birth_density’
   sp->sf_data.birth_density = 0.f;
              ^
make[3]: *** [libswiftsim_la-space.lo] Error 1
Makefile:1396: recipe for target 'libswiftsim_la-space.lo' failed