Update code to current post-10 branch

Latest commit on post-10 branch: e5dfbd4b23

src/bin/test-basic-boot.rs

@@ -1,6 +1,6 @@
-#![no_std] // don't link the Rust standard library
+#![cfg_attr(not(test), no_std)]
 #![cfg_attr(not(test), no_main)] // disable all Rust-level entry points
-#![cfg_attr(test, allow(dead_code, unused_macros, unused_imports))]
+#![cfg_attr(test, allow(unused_imports))]
 
 use blog_os::{exit_qemu, serial_println};
 use core::panic::PanicInfo;