Add fsync. Add env scheme, currently hardcoded to get ion to launch. Make serial IRQ send data to debug scheme

kernel/scheme/initfs.rs

@@ -78,6 +78,10 @@ impl Scheme for InitFsScheme {
         Err(Error::NotPermitted)
     }
 
+    fn fsync(&mut self, file: usize) -> Result<()> {
+        Ok(())
+    }
+
     fn close(&mut self, file: usize) -> Result<()> {
         self.handles.remove(&file).ok_or(Error::BadFile).and(Ok(()))
     }