First compile spinsfast as described in the package, remember to set the build
system variable.

Then use this
gcc -shared -Wl,-soname,libspinsfast.so.1 -lcfitsio -lfftw3 -lchealpix -lgsl -lgslcblas -o libspinsfast.so.1.0.1 ../spinsfastpy/spinsfast_rev90/obj/*.o
