science/orthanc: fix build on 32-bits

/wrkdirs/usr/ports/science/orthanc/work/Orthanc-1.12.3/OrthancFramework/Sources/Images/JpegWriter.cpp:199:5: error: no matching function for call to 'jpeg_mem_dest'

199 |     jpeg_mem_dest(&cinfo, &data, &size);
    |     ^~~~~~~~~~~~~

/usr/local/include/jpeglib.h:974:14: note: candidate function not viable: no known conversion from 'size_t *' (aka 'unsigned int *') to 'unsigned long *' for 3rd argument

974 | EXTERN(void) jpeg_mem_dest(j_compress_ptr cinfo, unsigned char **outbuffer,
    |              ^
975 |                            unsigned long *outsize);
    |                            ~~~~~~~~~~~~~~~~~~~~~~

1 error generated.