Merge pull request #17 from rofrol/patch-2

Missing extern crate panic_halt

src/getting-started/01.00.BUILD.md

@@ -149,6 +149,8 @@ Note, you would also need to disable [name mangling][nm]:
 #![no_std]
 #![no_main]
 
+extern crate panic_halt;
+
 #[no_mangle]
 pub extern "C" fn _start() -> ! {
     loop {}