another optimization work-around

Author: RalfJung

tests/compile-fail/unaligned_pointers/unaligned_ptr_zst.rs

@@ -2,8 +2,8 @@
 // compile-flags: -Zmiri-disable-validation
 
 fn main() {
-    for _ in 0..10 { // Try many times as this might work by chance.
-        let x = 2u8;
+    for i in 0..10 { // Try many times as this might work by chance.
+        let x = i as u8;
         let x = &x as *const _ as *const [u32; 0];
         // This must fail because alignment is violated. Test specifically for loading ZST.
         let _x = unsafe { *x }; //~ERROR alignment 4 is required