ASSERT in every app on ARM: opnd_t size changed

I assume this is a regression from PR #4467 3a408a03. Lack of ARM CI tests is really an issue.

95: <Application /home/derek/dr/git/build_dbg_tests/suite/tests/bin/client.signal (16492).  Internal Error: DynamoRIO debug check failure: /home/derek/dr/git/src/core/arch/arch.c:668 sizeof(opnd_t) == EXPECTED_SIZEOF_OPND