Rollup merge of #144996 - dianqk:simplifycfg-collapse_goto_chain-changed, r=cjgillot

simplifycfg: Mark as changed when start is modified in collapse goto chain

Split from rust-lang/rust#142771.
r? cjgillot

compiler/rustc_mir_transform/src/simplify.rs

@@ -225,6 +225,7 @@ impl<'a, 'tcx> CfgSimplifier<'a, 'tcx> {
             current = target;
         }
         let last = current;
+        *changed |= *start != last;
         *start = last;
         while let Some((current, mut terminator)) = terminators.pop() {
             let Terminator { kind: TerminatorKind::Goto { ref mut target }, .. } = terminator