Preparing for a rustc behavior change that'll happen soon

Author: RalfJung

tests/fail/intrinsics/ptr_offset_from_unsigned_neg.rs

@@ -1,4 +1,6 @@
 //@error-pattern: first pointer has smaller offset than second: 0 < 4
+// Preparing for a rustc behavior change that'll happen soon: (FIXME remove this after the next submodule bump succeeded)
+//@normalize-stderr-test: "`(ptr_offset_from_unsigned)`" -> "$1"
 #![feature(ptr_sub_ptr)]
 
 fn main() {