MSVC on x86 has issues with ALIGNAS(8) on InstructionOperand,
but does align the object to 8 bytes anyway. As a work-around,
avoid ALIGNAS for InstructionOperand on MSVC x86.

BUG=v8:10796

Change-Id: Iabb465489d97f9518a4429e8d78c06296539ed97
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2358680Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Commit-Queue: Ross McIlroy <rmcilroy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#69450}