[clang][test] Fix test issue under LLVM_REVERSE_ITERATION
The order of these items may not be the same if reverse iteration is
enabled. From what I can tell this is related to visitation order, and I
don't see an easy way to handle that using the typical solutions, like
MapVector, etc. For now, just use CHECK-DAG to get the test into a
passing state.
Fixes #167057