Add note to Rust example explaining why functions are missing in the …

…output

Rust issue: rust-lang/rust#119850

examples/rust/default.rs

@@ -1,4 +1,11 @@
 // Type your code here, or load an example.
+
+// As of Rust 1.75, small functions are automatically
+// marked as `#[inline]` so they will not show up in
+// the output when compiling with optimisations. Use
+// `#[no_mangle]` or `#[inline(never)]` to work around
+// this issue.
+#[no_mangle]
 pub fn square(num: i32) -> i32 {
     num * num
 }