[gardening] Skip dart/run_appended_aot_snapshot_test on simarm_x64
[gardening] Skip dart/run_appended_aot_snapshot_test on simarm_x64

This test assumes `gen_snapshot` is available in the build folder where
the test gets run from. Though simarm_x64 is special in that only
test.py knows about the location of the right `gen_snapshot`.

Therefore we skip this test on simarm_x64 (which is '$builder_tag ==
crossword").

Change-Id: I677c781a970dec358f593c4504051ac515d48d0f
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/116961
Reviewed-by: Martin Kustermann <a35dd5b79fac84b2bb3b026a16b8becc55af5961@google.com>

dart-lang/sdk,dart-archive/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dart-lang/sdk,dart-archive/dart-sdk,dartino/dart-sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dartino/dart-sdk,dart-archive/dart-sdk,dartino/dart-sdk,dartino/dart-sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dartino/dart-sdk,dart-lang/sdk,dart-lang/sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dart-lang/sdk