Fix error with `--cfg parallel_compiler`
Fix error with `--cfg parallel_compiler`

Apparently expansion() really does return Rc, not Lrc

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