[vm] Fix IL/disassembly output generation with -v
[vm] Fix IL/disassembly output generation with -v

https://dart-review.googlesource.com/c/sdk/+/261360 had a typo and
checked kernel result instead of snapshot result.

Example invocation:

    dart compile exe \
        --extra-gen-snapshot-options=--disassemble,--print-flow-graph,--print-flow-graph-filter=<function name> \
        -v <Dart file>

Change-Id: Ic5e540825874f44105579382b2b05dd710791206
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/261643
Reviewed-by: Slava Egorov <72c81f38df725d8f1832acb9b5bb99563fc2f1b9@google.com>
Commit-Queue: Slava Egorov <72c81f38df725d8f1832acb9b5bb99563fc2f1b9@google.com>

dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk