[DO_NOT_MERGE] Converting unsigned long to size_t

[datumbox]

Fixes #3775

[datumbox]

So now it fails with:

C:\Users\circleci\project\torchvision\csrc\io\image\cpu\encode_jpeg.cpp(77): error C2664: 'void jpeg_mem_dest(j_compress_ptr,unsigned char **,unsigned long *)': cannot convert argument 3 from 'size_t *' to 'unsigned long *'

Which is the opposite of what the original issue reported...

I believe that this is related to a known issue we've seen before. On Linux and MacOS size_t is unsigned long while on windows it's unsigned __int3264. Conda has a jpeg lib version that uses unsigned long and if we unpin the version we get this issue. The temporary solution introduced by @seemethere was to pin it. Not sure if that's preferred or if we should do a hacky/dodgy workaround of defining different type depending on platform.

[seemethere]

I think it should probably be fine to pin it if the version we pin to is usable for all of the platforms we support, although it's not a great long term solution.

A better long term solution would be to workaround the different types issues for each platform