H5system.c(482): error: identifier “errno” is undefined
errno = 0;
export CFLAGS="$CFLAGS -DH5_STDC_HEADERS" to your environment/the libconfigure script (somewhere before configure of HDF5) to fix this error. It makes sure HDF5 includes the system headers (including “errno.h”).
If you have issues with CGNS after that, try building it with CMake (either manually or adjust the libconfigure) — maybe the libconfigure already does that.
This should get it up and running 🙂