Separate codepaths for fat and thin LTO in write.rs
Separate codepaths for fat and thin LTO in write.rs

These are going to have different intermediate artifacts, so
create separate codepaths for them.

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