Add diagnostic translation lints to crates that don't emit them

compiler/rustc_fs_util/src/lib.rs

@@ -1,3 +1,6 @@
+#![deny(rustc::untranslatable_diagnostic)]
+#![deny(rustc::diagnostic_outside_of_impl)]
+
 use std::ffi::CString;
 use std::fs;
 use std::io;