Auto merge of #219 - Amanieu:sync_val_compare_and_swap, r=alexcrichton
Auto merge of #219 - Amanieu:sync_val_compare_and_swap, r=alexcrichton

Fix argument order for __sync_val_compare_and_swap

Fixes https://github.com/rust-lang/rust/issues/46822#issuecomment-353698138

japaric/rustc-builtins,japaric/rustc-builtins