Set bless output of MIR tests to panic=unwind

Make the default MIR test and bless output consistent.

Author: dianqk

src/bootstrap/src/core/build_steps/test.rs

@@ -1525,13 +1525,12 @@ You can add that mapping by changing MIR_OPT_BLESS_TARGET_MAPPING in src/bootstr
                 });
 
             for target in targets {
-                run(target);
-
                 let panic_abort_target = builder.ensure(MirOptPanicAbortSyntheticTarget {
                     compiler: self.compiler,
                     base: target,
                 });
                 run(panic_abort_target);
+                run(target);
             }
         } else {
             run(self.target);

tests/mir-opt/uninhabited_enum_branching.otherwise_t5_uninhabited_default.UninhabitedEnumBranching.diff

@@ -48,7 +48,7 @@
       }
 
       bb5: {
-          drop(_2) -> [return: bb6, unwind unreachable];
+          drop(_2) -> [return: bb6, unwind: bb7];
       }
 
       bb6: {
@@ -57,5 +57,9 @@
           _0 = const ();
           return;
       }
+  
+      bb7 (cleanup): {
+          resume;
+      }
   }