Do not run const prop on the mir_for_ctfe of const fn

src/test/ui/const_prop/ice-assert-fail-div-by-zero.rs

@@ -1,6 +1,8 @@
 // check-pass
 
-// compile-flags: --crate-type lib
+// need to emit MIR, because const prop (which emits `unconditional_panic`) only runs if
+// the `optimized_mir` query is run, which it isn't in check-only mode.
+// compile-flags: --crate-type lib --emit=mir,link
 
 #![warn(unconditional_panic)]
 

src/test/ui/const_prop/ice-assert-fail-div-by-zero.stderr

@@ -1,11 +1,11 @@
 warning: this operation will panic at runtime
-  --> $DIR/ice-assert-fail-div-by-zero.rs:11:5
+  --> $DIR/ice-assert-fail-div-by-zero.rs:13:5
    |
 LL |     f.0 / 0;
    |     ^^^^^^^ attempt to divide `_` by zero
    |
 note: the lint level is defined here
-  --> $DIR/ice-assert-fail-div-by-zero.rs:5:9
+  --> $DIR/ice-assert-fail-div-by-zero.rs:7:9
    |
 LL | #![warn(unconditional_panic)]
    |         ^^^^^^^^^^^^^^^^^^^

src/test/ui/consts/const-eval/issue-49296.stderr

@@ -4,7 +4,7 @@ error: any use of this value will cause an error
 LL | const X: u64 = *wat(42);
    | ---------------^^^^^^^^-
    |                |
-   |                pointer to alloc2 was dereferenced after this allocation got freed
+   |                pointer to alloc1 was dereferenced after this allocation got freed
    |
    = note: `#[deny(const_err)]` on by default