don't optimize prologs/epilogues in OptimizePostIndexed (#114843)

Author: EgorBo

src/coreclr/jit/emitarm64.cpp

@@ -17391,6 +17391,12 @@ bool emitter::OptimizePostIndexed(instruction ins, regNumber reg, ssize_t imm, e
         return false;
     }
 
+    if (emitComp->compGeneratingUnwindProlog || emitComp->compGeneratingUnwindEpilog)
+    {
+        // Don't remove instructions while generating "unwind" part of prologs or epilogs
+        return false;
+    }
+
     // Cannot allow post indexing if the load itself is already modifying the
     // register.
     regNumber loadStoreDataReg = emitLastIns->idReg1();