Remove example code as it does not compile in CI

Code is QNX/nto specific and will not link on Windows.

src/doc/rustc/src/platform-support/nto-qnx.md

@@ -32,7 +32,7 @@ QNX Neutrino toolchain).
 
 ### Small example application
 
-```rust
+```rust,ignore (platform-specific)
 #![no_std]
 #![no_main]
 #![feature(lang_items)]