Undo accidental test deletion in previous commit.

tests/compile-fail/static_memory_modification.rs

@@ -0,0 +1,9 @@
+static X: usize = 5;
+
+#[allow(mutable_transmutes)]
+fn main() {
+    unsafe {
+        *std::mem::transmute::<&usize, &mut usize>(&X) = 6; //~ ERROR: tried to modify constant memory
+        assert_eq!(X, 6);
+    }
+}