Auto merge of #33457 - oli-obk:const_err/cast_u8_ptr, r=eddyb

casting `&[u8]` to `* const u8` doesn't work in const_eval

fixes #33452

r? @eddyb

cc @Ms2ger

src/test/run-pass/const-err.rs

@@ -12,6 +12,7 @@
 
 #![deny(const_err)]
 
+const X: *const u8 = b"" as _;
 
 fn main() {
     let _ = ((-1 as i8) << 8 - 1) as f32;