Try fixing bigendian metadata serialisation
Try fixing bigendian metadata serialisation

I compiled this on PPC to check and it seems to work, but not sure whether I didn't mess up
anything in a major way.

Maybe a good shot at #41443

graydon/rust,aidancully/rust,aidancully/rust,graydon/rust,GBGamer/rust,graydon/rust,GBGamer/rust,GBGamer/rust,GBGamer/rust,graydon/rust,aidancully/rust,graydon/rust,GBGamer/rust,GBGamer/rust,graydon/rust,aidancully/rust,GBGamer/rust,GBGamer/rust,aidancully/rust,aidancully/rust